KR20090095338A - LED Lighting Device - Google Patents

Abstract

An LED lighting device is provided to implement various luminance manners by respectively controlling luminous intensities of RGB LEDs. A microprocessor(220) analyzes an inputted DMX data, and counts the number of control signals according to the inputted DMX data. The microprocessor outputs a control signal, and an LED driver(240) controls the LED operation by the control signal outputted from the microprocessor. The LED emits light according to the control of the LED driver.

Description

LED lighting device {LED Lighting Device}

The present invention relates to an LED lighting device, and more particularly, to an LED lighting device capable of controlling LED brightness of two or more colors by counting the number of control signals (pulses) output from a microcontroller.

The present invention can be used universally in the brightness control of lighting equipment using LEDs driven in various ways.

LED (Light Emitting Diode) can express all colors of nature using red, green, and blue, and it has various colors due to the advantages of eco-friendly, low power consumption and semi-permanent. It is widely used for producing directing lighting.

LEDs can be expressed in a variety of colors using red, green, and blue, and are widely used for various production lighting.

Conventional LED lighting control method uses a lot of DMX (Digital Multiplex) control method, DMX control method means a digital multiplexer signal and is the most common international standard standard used with the light source-related equipment.

DMX, short for DMX512, uses RS-485 communication over two wires to transmit data at 250.000 bits per second (250kbps) and provides 512 channels per data link.

In the conventional LED lighting device, a DMX controller generating a DMX control signal and a plurality of LED lighting devices are connected to each other using a daisy-chain method.

According to the DMX communication standard, the DMX controller has 512 consecutive start bits (Start bit: 1 bit), data bits (Data bit: 8 bits), and stop bit (2 bits) as one packet. Send the packet to the LED luminaire.

Each LED lighting device has a unique address (unique address), and receives a data code of a corresponding packet and uses the same to control lighting.

Since the DMX data is 8 bits, the LEDs can be adjusted in 256 (0 to 256) steps in total, and 16,777,215 (256 ³ -1) colors can be achieved when using RGB LEDs.

The method of driving the LED driver may be configured by various methods, and FIG. 1 illustrates a method of driving the LED driver.

Figure 1a is a method using a resistor as a current limiting device, in this case there is a disadvantage that the brightness of the LED changes according to the change of the input voltage.

FIG. 1B illustrates a method of configuring a constant current circuit using a regulator, and FIG. 1C illustrates a method of configuring a constant current circuit using a transistor. 1B and 1C form a constant current circuit, there is an advantage that a uniform LED brightness can be obtained when the input voltage is higher than the LED driving voltage by a predetermined voltage, but the input voltage and the driving voltage for driving the LED with a constant current. There is a disadvantage in that power is generated due to the device that is in charge of the constant current by the difference voltage (the driving voltage for driving the input voltage-LED with the constant current).

FIG. 1D may control a constant current to flow through the LED with high efficiency by switching an input voltage using a switching element such as a transistor or a field effect transistor (FET). Therefore, such a circuit is mainly used for power LEDs of 1W or more and has an advantage of good efficiency, but has a disadvantage in that the circuit configuration is complicated and expensive.

Sending a control signal to the LED driver circuit as described above A method of controlling a direct current (DC) continuous current and a method of controlling a pulse current are used a lot. It is desirable to control the DC continuous current to provide the light output suitable for the human eye, but it has the disadvantage of slow response time and poor resolution. The pulse current control method based on the modulation method (PWM, Pulse Width Modulation) is used.

Figure 2 shows the output signal by the conventional pulse width modulation (PWM) method.

Referring to FIG. 2, the conventional pulse width modulation (PWM) method maintains a constant output period of a microcontroller, divides the period by 0 to 255, and adjusts the pulse width in 256 steps. It is a step-by-step control from 0% to 100%.

When controlling by the conventional pulse width modulation (PWM) method, the output signal is individually controlled by each independent duty cycle in which a predetermined period is divided into 256 steps, thereby controlling the brightness of 256 steps per LED. Therefore, when the duty cycle reaches 255 steps, the LED light output is 100%.

However, the conventional pulse width modulation (PWM) method has a limit in controlling the current flowing through the LED, and when additional functions such as temperature control are added, there is a limit in lighting.

In order to solve the above problems, an object of the present invention is to provide a microcontroller with a different frequency of red, green, and blue LEDs having a constant frequency according to an input voltage. The present invention provides an LED lighting device that outputs a control signal and counts the number of control signals (pulses) corresponding to each duty to reduce power consumption generated in the LED driver circuit and has various additional functions.

In order to achieve the above object, the LED lighting apparatus according to the present invention analyzes the input DMX data, and counts the number of control signals (number of pulses) according to the input DMX data and outputs a control signal. The control signal output from the microprocessor is characterized in that it comprises an LED driver for controlling the operation of the LED and the LED to emit light under the control of the LED driver.

Here, the LED is characterized in that it comprises two or more LEDs selected from among the red (RED), green (Green) and blue (BULE) LEDs.

When the power consumption of the LED driver is a problem, the microcontroller outputs control signals of different duty ratios having a predetermined frequency to each of the two or more LEDs.

In addition, the microcontroller measures the forward voltage value of each color of the RGB LED and the PWM controller that controls the pulse which is a control signal corresponding to the DMX data, and the duty of each RGB LED so that the average current set in each RGB LED flows. A duty ratio calculation module for calculating the ratio D, an output comparison register for storing the register value N calculated from the duty ratio calculation module, and a pulse generated from the PWM controller to have a duty ratio stored in the output comparison register And a coefficient register for counting the number of pulses each time a pulse controlled by the duty ratio control module occurs.

The coefficient register is

The coefficient register compares the data value of each RGB LED received through DMX data with the counter value, and if it matches, disables the output of the PWM controller, and when the register value reaches 255, newly receives DMX data. Update and reset, and if the received data of the RGB LED is not 0, the output of the PWM controller (Enable) is characterized in that (Enable).

In addition, the duty ratio calculation module is characterized in that when the LED driver is configured as a constant current circuit, the LEDs of two or more colors are set to the same duty ratio.

The coefficient register is configured separately for each of the RGB LEDs to process the DMX data.

As can be seen through the above problem solving means, the LED lighting device according to the present invention can not only prevent heat generation and power loss due to overcurrent of the LED driver driving circuit, but also independently stabilize the luminance of each of three color RGB LEDs. It can be controlled to produce an excellent effect that can produce a variety of lighting.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a system configuration of the LED lighting apparatus according to a preferred embodiment of the present invention, Figure 4 is a block diagram of the LED lighting apparatus according to a preferred embodiment of the present invention, Figure 4 is a block diagram of the microcontroller of Figure 5 to be.

3 to 5, the LED lighting apparatus according to the present invention includes a plurality of LED lighting apparatuses 1 to N connected to an address inputter 10 for inputting an address and the daisy-chain method with the address inputter 10. Can be configured to include 20). Here, the number of the LED lighting device 20 is connected to the address input unit 10 may be freely set within the limit that can be transmitted packet according to the purpose of the lighting direction.

The address input unit 10 and the plurality of LED lighting units 20 are connected to two power lines V + and GND, two communication lines DMX + and DMX- and one address line Address_in or Adderss_out. Here, the power line may be used for the power supply of the LED lighting device 20 together with the role of a power source for driving the address input unit 10, the communication line is connected according to the DMX512 standard and the address input unit 10 and the LED It is used to transmit and receive data between the luminaires 20, and the address line is used to switch to a state in which each LED luminaire can receive an address input.

The address output address_out of the address input unit 10 is connected to the address input ADDR_IN of the first LED luminaire, and the address output ADDR_OUT of the first LED luminaire is connected to the address input ADDR_IN of the second LED luminaire. . In the above method, the address line is connected to the Nth LED luminaire.

Hereinafter, since the configuration of the address input unit 10 deviates from the core of the present invention, a detailed description thereof will be omitted.

The LED lighting device 20 includes a microcontroller 220 for controlling the entire LED lighting device, a transceiver 230 through which DMX data is input / output, and a voltage at which the microcontroller can stably drive an input voltage (+ 5V). Regulator 210 for converting to the microcontroller generates a clock that can operate the microcontroller 250 to receive the asynchronously input communication data stably to control the LED driver smoothly, to the control signal by the microcontroller It may be configured to include an LED driving circuit 240 for controlling the LED drive by and the LED 260 operated by the LED driving circuit.

Here, the transceiver 230 converts the DMX 512 (RS-485) signal input through the connector IN to a signal that can be recognized by the microcontroller, and then transmits an output signal to the microcontroller 220, and the microcontroller 220 ) Controls the LED 250 by driving the LED driver 240 by analyzing a communication signal transmitted through the transceiver 230.

The microcontroller 220 analyzes the DMX data transmitted through the transceiver, calculates and outputs a duty ratio having a predetermined frequency in each of two or more LEDs, and outputs a control signal of the duty ratio according to the input data. The control signal is output by counting the number of pulses.

More specifically, the microcontroller 220 measures the forward voltage value of each color of the RGB LED and the PWM controller 221 for controlling the pulse which is a control signal corresponding to 8-bit data, and sets the average current of each RGB LED. The duty ratio calculation module 222 that calculates the duty ratio of each RGB LED so as to flow, the output comparison register 223 that stores the value calculated from the duty ratio calculation module, and the pulse generated by the PWM controller are compared with the output ratio. A duty ratio control module 224 for controlling on / off to have a duty ratio stored in the register and a coefficient register 225 for counting the number of pulses each time a pulse controlled by the duty ratio control module occurs. Can be. The coefficient register 225 may be configured separately for each of the RGB LEDs to process the DMX data.

Hereinafter, a look at the LED lighting device control method according to the present invention configured as described above.

In the present invention, ATMEL ATMEGA48 is used as the microcontroller 220, and 20MHz crystal is used. In this embodiment, 8-bits are used as the PWM controller 221 to reduce the load of the microcontroller and smoothly generate a pulse control signal. PWM mode was used.

6A is a block diagram showing a case where a resistor is used as a current limiting device according to a preferred embodiment of the present invention.

First, measure the input voltage input to the LED lighting device.

Referring to FIG. 6A, the input voltage is divided by resistors R1 and R2, measured using an analog / digital converter (A / D conveter, not shown) of a microcontroller, and the measured voltage value is measured by an internal resistor (not shown). ). The analog / digital converter may be included in a duty ratio calculation module and may be separately configured in a microcontroller.

In this case, the reference voltage during analog / digital conversion is used as the input voltage of the microcontroller, but when a more precise analog / digital conversion data value is desired, an external reference voltage can be used.

The duty ratio of each of the RGB LEDs (red / green / blue LEDs) is then calculated.

More specifically, the duty ratio calculation module 222 calculates a desired average current for each of the RGB LEDs based on the total forward voltage values of the RGB LEDs connected in series with the resistance values of the resistors R3, R4, and R5 by the voltage measurement. It calculates the duty ratio of each RGB LED to flow. Here, the duty ratio refers to the duration of a pulse when a pulse is divided into 255 steps. For example, if the duty is 60, the duty ratio is? 0.23 since the pulse lasts for 60/256. .

In addition, an integer value of a value obtained by multiplying the value (duty value) calculated by the duty ratio calculation module by 255 is stored in each output comparison register. Here, since excessive pulse current should not flow through the LED, it is preferable to adjust the resistance values R3, R4, and R5 so that the value of the output comparison resistor has a value between 200 and 255. This prevents excessive pulse current from flowing through the LED, and at the same time, allows the microcontroller 222 to perform other tasks.

Looking at the duty ratio calculation process in more detail as follows.

The LED's forward voltage varies slightly from manufacturer to manufacturer, but is typically 2.0 to 2.2V for red LEDs and 3.1 to 3.3V for green and blue LEDs. The maximum forward current that can flow through the LED also varies depending on the type and manufacturer, but 35mA for high brightness LEDs and less than the maximum forward current when designing an actual LED circuit. .

7A is a circuit diagram for explaining LED forward current control.

Referring to FIG. 7A with reference to the red LED, resistors R1 and R2 are used to limit the current flowing in the LED, and five red LEDs are connected in series with the resistors R1 and R2, and to control the illumination of the LED. The circuit was constructed using the transistor which is a semiconductor switching element.

The current limiting resistors R1 and R2 can be calculated by the following Equation 1.

Where V _in : input voltage, N = number of LEDs, V _LED = forward voltage of LED

V _CE : Collector-Emitter Saturation Voltage of Transistor Q1

Figure 7b shows a state in which the LED lighting device is connected to the power supply.

When the LED lighting device is connected to the power supply as shown in FIG. 7B, the input voltage is changed according to the resistance value of the power supply line and the total amount of current flowing through the power supply line.

If the input voltage changes from 20V to 24V, the current flowing through the LED is 20mA, and the forward voltage of the LED is 2.1V, then the resistors R1 and R2 are calculated (assuming VCE = 0.3V).

Since the calculated R is 460Ω, the LED current value measured when R1 is 220Ω and R2 is 240Ω, and the calculated value through Equation 1 are shown in Table 1.

Input voltage (Vin) LED current (mA) Duty ratio (D) Register value (N) Measure Calculation 19 V 18.4 17.8 One 255 20 V 20.4 20.0 One 255 21 V 22.5 22.2 0.901 230 22 V 24.5 24.3 0.823 210 23 V 26.5 26.5 0.755 193 24 V 28.7 28.7 0.697 178

It can be seen from Table 1 that there is no significant difference between the measured value and the calculated value of the LED current. When the input voltage is 24V, the current flowing through the LED is different from the design value, which reduces the LED reliability and increases the brightness of the LED. Therefore, the above problems can be solved by reducing the average current flowing through the LED.

8 shows a pulse when a current flows.

Referring to FIG. 8, the average current i _ave may be calculated through Equation 2 below.

Where, i: current flowing through the LED, T: period, T _ON: ON time

D: Duty Ratio (T / T _ON )

Here, if the output comparison register has a variation range from 0 to 255, the register value for controlling the average current flowing through the LED is calculated as follows.

Register value (N) = integer value of (D × 255)

As a result, the duty ratio according to the average current may be calculated through Equation 2, and the value stored in the output comparison register may be calculated as shown in Table 1 by the duty ratio.

As shown in Table 1, by changing the register value to change the pulse of the control signal of the LED, it is possible to control the current flowing through the LED, and at the same time the illumination can be produced by the number of pulses. In addition, a low pass filter as shown in FIG. 9 may be configured to reduce the pulse current flowing through the LED.

As LEDs increase in temperature, breakage of the internal LED chip may occur, and reliability decreases as the brightness decreases over time. Therefore, if the temperature of the LED rises, there is a need for a method of reducing the temperature.

However, the conventional PWM control method needs to reduce the pulse width (duty width) to control the temperature rise of the LED, but when the pulse width is decreased (for example, when 255 is reduced to 240 as shown in FIG. 10), the maximum is achieved. Since the expression value that can be controlled is reduced (0 to 240), the expression is limited. However, the present invention reduces the pulse width and counts the number of pulses for temperature control. It is possible to produce a lighting effect.

Figure 6b is a circuit that can calculate a more accurate average current is possible to fine-tune the duty ratio by analog-to-digital conversion of the current flowing through the resistor R6.

When fine adjustment of the duty ratio is possible only by analog / digital conversion, the peak and hold circuit and the amplification circuit may be replaced by a low pass filter as shown in FIG. 6C.

The duty ratio control module 224 smoothly turns on / off a pulse control signal having a duty ratio stored in the output comparison register at a time when the pulse generated by the PWM controller 221 overflows. To control.

The count register 224 is then initially reset, and each time one pulse occurs, that is, each time a Timer / Count overflow occurs, the value of the count register is increased by one.

If the coefficient register 224 compares the data of each of the RGB LEDs received through DMX512 data and matches, disables the 8-bit PWM mode of the matching LEDs.

When the count register 224 becomes 255, the newly received DMX512 data is updated and the count register 224 is reset.

Subsequently, when the received data of the RGB LED is not 0, the 8-bit PWM mode of the corresponding LED is enabled.

, Where a method of turning off the output pulse control signal (OFF) can be made by entering a zero in the output compare register responsible for PWM, can each LED to the coefficient register set aside to handle DMX512 data.

In addition, the analog-to-digital conversion measurements can be updated using the free running mode or periodically.

11 is a waveform diagram of a control signal according to a preferred embodiment of the present invention.

LED forward voltages vary slightly from manufacturer to manufacturer, but are roughly 2.1V for red LEDs and 3.3V for green and blue LEDs. Therefore, the input voltage applied to the LED must be applied to a voltage greater than the sum of each of the green or blue LEDs connected in series. In this case, a greater power consumption occurs in the constant current circuit used for the red LED. Especially with 100% duty cycle, the highest power consumption occurs.

Therefore, the microcontroller 222 outputs control signals of different duty ratios having a constant frequency to the red LED, the green LED, and the blue LED according to the input voltage, thereby reducing power consumption generated in the LED driver circuit. Here, when the power consumption of the constant current circuit is not a problem, it is possible to output a control signal of the same duty ratio, and to control the LED brightness by the number of control signals (number of pulses).

That is, the luminance of the RGB LED according to the control signal of the DMX512 may be controlled in 256 steps from 0 to 255 through the coefficient of the control signal output from the microcontroller 222.

As can be seen in FIG. 11, since the duty ratio stored in the output comparison register 223 of the RGB LED is 180 for each of the red LEDs, and the DMX data transmitted in the first cycle is 2, the microcontroller generates two pulses having a duty ratio of 180. The counting (1-2 cycles) and the remaining cycles (3-255 cycles) are controlled to be off. Subsequently, since the DMX data of the next cycle (second cycle) is 255, the output is controlled by counting 255 pulses having a duty ratio of 180 (1-255 cycles).

In addition, since the duty ratio of the green LED is 220 and the DMX data transmitted in the first cycle is 128, the microcontroller 222 counts 128 pulses having a duty ratio of 220 (1-128 cycles) and the remaining cycles (129-255). Cycle) is controlled to be off. Subsequently, since the DMX data of the next cycle (second cycle) is 120, 120 pulses having a duty ratio of 220 are counted (1-120 cycles) and the remaining cycles (121-255 cycles) are controlled and outputted.

Finally, since the duty ratio of the blue LED is 250 and the DMX data transmitted in the first cycle is 255, the microcontroller 222 counts (255 cycles) 255 pulses having a duty ratio of 250 to control the output. Subsequently, since the DMX data of the next cycle (second cycle) is zero, the control is performed so that a pulse is not output.

As a result, the present invention is characterized in that the operation of the LED driver is controlled by calculating different duty ratios for each of the RGB LEDs and controlling the number of pulses corresponding to the transmitted DMX data to be output.

12 is a block diagram using a linear constant current circuit according to another embodiment of the present invention.

The constant current circuit can be configured using a regulator, a switching element, or a constant current integrated circuit. When many LED lighting devices are connected to one input voltage due to the configuration of the LED lighting device, the input voltage may fluctuate greatly depending on the lighting direction.

In this case, when the control is connected only with a resistor as shown in FIG. 6, the response speed of the control signal according to the change in the input voltage is slow, and thus, the constant current circuit as shown in FIG. 8 may be used to compensate for this.

Generally, the current value of the LED of the constant current circuit is designed as an average value. In this case, the value of the output comparison resistor can be fixed to 255. When using constant current circuits, there is no reason to measure the input voltage, which has the advantage that the microcontroller may want to do something else.

Fig. 13 shows a case of driving a power LED of 1W or more. In this case, driving efficiency is important because 350mA ~ 700mA current flows through the LED. When a power LED of 1W or more is configured as shown in FIG. 8, the circuit configuration can be simplified and the configuration cost can be lowered, but significant heat generation and efficiency degradation occur.

Therefore, when using the existing power LED driving circuit and the present invention as shown in FIG. 13, the value of the output comparison register is fixed to 255, and can be configured using a current mode PWM controller IC or an LED dedicated driver.

In addition, by using a temperature measuring device such as NTC (Negative Coefficient Thermistor) as shown in Figure 14 to improve the reliability of the LED by measuring the temperature of the LED by an analog / digital converter of the microcontroller, and reducing the value of the output comparison resistor At the same time, the brightness of the LED can be controlled in 256 steps from 0 to 255.

Although the detailed description of the present invention described above has been described with reference to the preferred embodiment of the present invention, the protection scope of the present invention is not limited to the above embodiment, and those skilled in the art will appreciate It will be understood that various modifications and changes can be made in the present invention without departing from the spirit and scope of the invention.

1 illustrates a method of driving an LED driver.

Figure 2 shows the output signal by the conventional pulse width modulation (PWM) method.

Figure 3 is a system configuration of the LED lighting apparatus according to a preferred embodiment of the present invention, Figure 4 is a block diagram of the LED lighting apparatus according to a preferred embodiment of the present invention, Figure 4b is a block of the microcontroller of Figure 5 It is also.

6A is a block diagram showing a case where a resistor is used as a current limiting device according to a preferred embodiment of the present invention.

7A is a circuit diagram for explaining LED forward current control.

Figure 7b shows a state in which the LED lighting device is connected to the power supply.

8 shows a pulse when a current flows.

9 is a circuit diagram of an LED driver including a low pass filter.

10 is an exemplary waveform diagram of a conventional PWM control method.

11 is a waveform diagram of a control signal according to a preferred embodiment of the present invention.

12 is a block diagram using a linear constant current circuit according to another embodiment of the present invention.

Fig. 13 is a circuit diagram when driving a 1W or higher power LED.

14 is a circuit diagram of an LED driver including a negative coefficient thermistor (NTC).

* Description of the symbols for the main parts of the drawings *

10: address input device 20: LED lighting device

210: regulator 220: microcontroller

230: transceiver 240: LED driver

250: Crystal 260: LED

Claims (7)

A microprocessor for analyzing the input DMX data, counting the number of control signals (number of pulses) according to the input DMX data, and outputting a control signal; An LED driver for controlling the operation of the LED to the control signal output from the microprocessor; LED lighting device comprising a light emitting LED according to the control of the LED driver. The method of claim 1, The LEDs LED lighting device comprising at least two LEDs selected from among the red, green, and blue LEDs. The method of claim 2, The microcontroller If the power consumption of the LED driver is a problem LED control device, characterized in that for outputting a control signal of each different duty ratio having a constant frequency to each of the two or more LEDs. The method of claim 3, wherein The microcontroller A PWM controller controlling a pulse which is a control signal corresponding to the DMX data; A duty ratio calculation module for measuring a forward voltage value of each color of the RGB LEDs and calculating a duty ratio D of each RGB LED such that an average current set in each RGB LED flows; An output comparison register for storing a register value N calculated from the duty ratio calculation module; A duty ratio control module configured to control on / off so that a pulse generated by the PWM controller has a duty ratio stored in the output comparison register; And a coefficient register for counting the number of pulses each time a pulse controlled by the duty ratio control module occurs. The method of claim 4, wherein The count register is Compare and counter the data value of each RGB LED received through DMX data and disable the output of the PWM controller. When the register value is 255, the newly received DMX data is updated and reset, and if the received data of the RGB LED is not 0, the LED luminaire, characterized in that (Enable) enable the output of the PWM controller. The method of claim 4, wherein The duty ratio calculation module And the LED driver is configured as a constant current circuit, wherein the two or more LEDs are set to the same duty ratio. The method of claim 4, wherein The count register is LED lighting device, characterized in that configured separately for each of the RGB LED to process the DMX data.

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