JP2012212550A - Led light emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED light emission control device capable of achieving an emission having a fluctuation closer to nature (for example, a fluctuation of a candle flame) in LED light emission control.SOLUTION: An LED light emission control device comprises: luminance data holding means 110 for holding digital data representing a luminance of light; luminance data reading means for sequentially reading the digital data; ΔΣ processing means 120 for performing ΔΣ processing for the read digital data with a program operating on a microcomputer; high-frequency noise removal means for removing a high-frequency noise from the data demodulated by the ΔΣ processing means 120; and LED light emission means for causing the LED to emit light based on the data from which the high-frequency noise is removed.

Description

  The present invention relates to an LED (light emitting diode) light emission control device, and more particularly, to an LED light emission control device capable of reproducing spontaneous light emission, such as candle light, which could not be realized by conventional LED light emission control.

  In recent years, LEDs (light-emitting diodes) have long lifespans and can save power, so that they are used in various applications such as backlights for liquid crystal displays in addition to lighting instead of incandescent bulbs. Yes. In general, a PWM (pulse width modulation) method is used for LED brightness control (dimming). However, PWM control is a dimming method that uses a human visual afterimage, and when the on-duty time is shortened, the blinking of the LED becomes conspicuous rather than the brightness control. Patent Document 1 discloses a technique for switching to dimming using an analog signal.

JP 2008-210537 A

  In the technique of Patent Document 1, since there is still a part that performs PWM control, when there is a part where the brightness changes abruptly (for example, fluctuation of the flame of a candle), light emission that reproduces it naturally Is difficult to realize.

  The present invention has been made in view of the above points, and an LED light emission control device capable of realizing light emission with more natural fluctuations (for example, candle flame fluctuations) in the light emission control of LEDs. The purpose is to provide.

  In order to solve the above problems, an LED light emission control device according to the present invention reads luminance data holding means for holding digital data representing the luminance of light, luminance data reading means for sequentially reading the digital data, and reading With respect to the digital data, a ΔΣ processing means for performing ΔΣ processing by a program operating on a microcomputer, a high frequency noise removing means for removing high frequency noise from the data demodulated by the ΔΣ processing means, and high frequency noise are removed. LED light emitting means for causing the LED to emit light based on the data.

  The high-frequency noise removing unit can be configured by a secondary LPF. Furthermore, it can also be set as the structure provided with the brightness | luminance data generation means which produces | generates the digital data showing the said brightness | luminance from natural light.

  The LED light emission control device according to the present invention produces an effect that natural light such as candle light can be reproduced by the LED.

It is a figure for demonstrating an example of the whole schematic structure of the LED light emission control apparatus in embodiment of this invention. In this Embodiment, it is a figure for demonstrating the method to acquire luminance data. 6 is a flowchart for explaining an example of processing contents of the microcomputer 100 including a ΔΣ processing unit 120; It is a flowchart for demonstrating an example of the specific content of a main process. It is a figure which shows the voltage of the brightness | luminance data obtained from the light of the candle as an example of natural light. It is a figure which shows the voltage of the light reproduced in the LED light emission control apparatus of this Embodiment. It is an enlarged view which shows a mode that both were piled up.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining an example of an overall schematic configuration of an LED light emission control device according to an embodiment of the present invention.

  The LED light emission control of the present embodiment is mainly realized by a computer program that operates on the microcomputer 100. As the microcomputer 100, specifically, a PIC16F88 manufactured by Microchip can be used, and a so-called PIC microcomputer is advantageous in terms of cost because it is cheaper than other high-spec CPUs. The range that can be protected by the present application is not limited to the PIC microcomputer.

  As the power supply unit 200, for example, a battery of 12 V can be used, or a power source obtained by converting a commercial power source into a DC power source using an AC adapter, a power source for operating the microcomputer 100, and LEDs 300 a to 300 d can be used. Supply drive power.

  The power supply unit 200 includes a power switch 210. When the power switch 210 is turned on, power is supplied and a program stored in the microcomputer 100 operates. The voltage adjustment unit 220 includes a three-terminal regulator, for example, and adjusts the voltage of the power supply of the power supply unit 200 to an appropriate value.

  The microcomputer 100 includes a luminance data holding unit 110, a ΔΣ processing unit 120, and a luminance data output unit. The luminance data holding unit 110 holds luminance data (digital data) for causing the LED to emit light. FIG. 2 is a diagram for describing a method of acquiring luminance data in the present embodiment.

  For example, light from a natural light source such as a candle 600 (not limited to a candle) is received by a phototransistor 710 (which may be a photodiode) and AD converted by an A / D converter 720. The luminance data holding unit 110 holds the digital data. The luminance data holding unit 110 may be a memory inside the microcomputer 100 or an external memory.

  Since the PIC16F88 has a 10-bit A / D converter function, the luminance data (digital data) obtained from natural light such as the candle 600 may be stored in the memory using this. However, the A / D converter may be externally attached instead of the one inside the microcomputer. For example, in this embodiment, data of voltage change of the phototransistor 710 is collected with a digital oscilloscope (WJ312 manufactured by LeCroy).

The sampling period at this time is 10 ⁻⁴ (seconds), that is, 0.1 milliseconds and 10 kHz sampling. In this embodiment, in order to reproduce a steep change in natural light, the received light data is captured by the luminance data holding unit 110 by high-frequency sampling, but the capture timing is not limited to the above.

  Returning to FIG. 1, the reproduction of the obtained luminance data by the LEDs 300a to 300d will be described. The number of LEDs, color (wavelength), etc. are not limited.

  In the present embodiment, ΔΣ processing is performed by software on the luminance data stored in the luminance data holding unit 110 by the ΔΣ processing unit 120. A modulation method that changes the pulse density in accordance with the output voltage is called ΔΣ modulation. The ΔΣ-modulated pulse is demodulated into an analog signal through a low-pass filter (LPF).

  In the present embodiment, digital data held in the luminance data holding unit 110 is converted into a format suitable for LED light emission control using the function of the microcomputer. FIG. 3 is a flowchart for explaining an example of processing contents of the microcomputer 100 including the ΔΣ processing unit 120.

  When power supply to the microcomputer 100 is started, initial setting is first performed (S101). In the initial setting, processing such as initialization of a memory area in the microcomputer 100 is executed.

  Next, timer interrupt setting is performed (S102). The timer interrupt timing set here can be set to 16.8 μs, for example, but is not limited thereto, and the interrupt timing is set in accordance with the sampling timing of the luminance data held in the luminance data holding unit 110. It can be set arbitrarily.

  If the timer interrupt timing comes (S103: Yes), the process proceeds to the main process (S104). FIG. 4 is a flowchart for explaining an example of specific contents of the main process.

  In the main process, the luminance data (digital data) held in the luminance data holding unit 110 is read (S201). In this case, reading is performed with 8 bits of luminance data every timer interruption time.

  Next, it is determined whether the counter value exceeds 255 (S202). As the counter, a counter provided in the microcomputer 100 can be used. If the counter value does not exceed 255 (S202: No), the output port of the microcomputer 100 is set to 0. Accordingly, no voltage is output from the port (S203). If the counter value exceeds 255 (S202: Yes), the output port of the microcomputer 100 is set to 1, and a voltage of 5V is output from the output port of the microcomputer (S204).

  When a voltage of 5V is output, 255 is subtracted from the counter value (S205). Then, luminance data (0 or 1) is added to the counter value (S206). It is determined whether or not the number of interrupts exceeds 255 (S207). If the number of interrupts exceeds 255 (S207: Yes), the next luminance data (0 or 1) is read (S208).

  Through the processing as described above, a voltage of 5 V is output from the output port of the microcomputer 100 as appropriate. However, for example, in order to reproduce the smoothness of an analog signal such as the light of the candle 600, it is necessary to sample at a high frequency, and the output of the ΔΣ processing unit 120 includes a lot of quantization noise. . Therefore, in this embodiment, the LPF has a quadratic form.

The primary LPF of the present embodiment includes a resistor 510 and a capacitor 520. For example, the resistance value of the resistor 510 is as large as 4 k ohms, the capacitance of the capacitor 520 is as small as 0.1 μfarad, and the time constant is 0.4. * ^10-3 , and the second-order LPF is composed of a resistor 530 and a capacitor 540. For example, the resistance value of the resistor 530 is reduced to 1 k ohms, the capacitance of the capacitor 540 is increased to 2.2 μfarad, and the time constant 2. It was set to 2 * ^10-3 . The resistance value and the capacitance value of the capacitor are not limited to this.

  In general, since the luminance of the LED is not linear with respect to the input voltage, in order to adjust the bias current of the base to an appropriate value for driving the LED by the transistor 410, in this embodiment, the luminance is adjusted by the variable resistor 420. Yes.

  FIG. 5 is a voltage of luminance data obtained from a candle light as an example of natural light, and FIG. 6 is a diagram illustrating a voltage of light reproduced in the LED light emission control device of the present embodiment. FIG. 7 is an enlarged view showing a state in which both are superimposed.

  As described above, it has become clear that natural light can be reproduced by the LED light emission control device of the present embodiment. In the above description, the case where natural light from the candle 600 or the like is converted into luminance data and reproduced by the LED has been described. However, the luminance data is not necessarily acquired from a natural light source. Good. That is, arbitrary LED light emission control can be realized by separately creating luminance data. In general, the light emission of the LED is not linear with the current value, but the LED light emission control according to the present embodiment can realize linear light emission control.

  Moreover, it can implement | achieve at low cost by performing LED light emission control using the microcomputer 100 like the said embodiment. Further, since smooth dimming of the LED is possible, it is extremely suitable for use as illumination and illumination, or for a liquid crystal backlight.

  The present invention can be applied to, for example, LED light emission control.

100 microcomputer 110 luminance data holding unit 120 ΔΣ processing unit 130 luminance data output unit 200 power supply unit 210 power switch 220 voltage adjustment unit 300a to 300d LED (light emitting diode)
410 Transistor 420 Variable resistance 510, 530 Resistance element 620, 640 Capacitance element

Claims (3)

Luminance data holding means for holding digital data representing the luminance of light;
Luminance data reading means for sequentially reading the digital data;
ΔΣ processing means for performing ΔΣ processing on the read digital data by a program operating on a microcomputer;
High-frequency noise removing means for removing high-frequency noise from the data demodulated by the ΔΣ processing means;
An LED light emission control device comprising: LED light emission means for causing an LED to emit light based on data from which high frequency noise has been removed. The high frequency noise removing means includes
The LED light emission control device according to claim 1, comprising a secondary LPF. further,
The LED light emission control device according to claim 1, further comprising a luminance data generation unit that generates digital data representing the luminance from natural light.

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