KR20050049913A - Circuit for driving led and method for driving the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit and a driving method of a light emitting diode capable of implementing a full color and a graphic equalizer using a voice signal, and comprising: first, second, and third light emission for emitting red, green, and blue light A diode, a first, second and third control current source for adjusting a current flowing through each of the first, second and third light emitting diodes according to a control signal, and converting each digital input signal into an analog signal and It is comprised with the 1st, 2nd, 3rd digital-analog converter which applies a control signal to a 1st, 2nd, 3rd control current source.

Description

Light-emitting diode driving circuit and driving method for small devices {Circuit for driving LED and method for driving the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit and a driving method of a light emitting diode which displays on / off of a power supply in a small device and is used as a backlight of a flat panel display device. It is about a method.

In general, in small devices such as mobile phones and MP3s, light emitting diodes (LEDs) are most often used to display power on / off, device status, operation status, and the like.

That is, the LED is turned on / off or blinking to display the power on / off, the status of the device, the operation status, or the keypad keyboard of a mobile phone or a small device such as an MP3. Make it easy to use the device in the dark.

In addition, in small devices, a flat panel display device such as a liquid crystal display device is used as a display means. The liquid crystal display device fills a liquid crystal between two substrates and displays an image according to the intensity of an electric field applied to the liquid crystal. In the liquid crystal display, since there is no means for emitting light by itself, it uses natural light or back light. LEDs are used as such backlights.

Therefore, a large number of LEDs are used in a small device, and may also be configured in various forms of display according to the characteristics of the device or the intention of the designer, and a combination of LEDs having different colors of light emitting different colors to produce various colors. It can also be configured.

At present, the method for changing the light is to combine the different light emitting LEDs and then adjust the color by adjusting the current flowing through each LED.

The most common method of color adjustment is to switch (ON / OFF) the current flowing through two or three light-emitting LEDs to make two colors (using two-color LEDs) or seven colors (using three-color LEDs). It is common to use to the extent.

This conventional LED driving circuit will be described with reference to the accompanying drawings as follows.

1 is a driving circuit diagram of a general light emitting diode.

In general, the LED driving circuit which is most widely used, by turning on or off the light emitting diode (LED) according to the presence or absence of a signal to display the operating state of the power supply of the device.

That is, as shown in FIG. 1, the most common light emitting diode driving circuit connects a light emitting diode (LED) and a switching transistor TR in series between a power supply terminal and a ground terminal to supply an input signal to the base of the switching transistor TR. The switching transistor TR is turned on / off by applying a power applied to a terminal to the light emitting diode LED.

Referring to the operation of the driving circuit of the general light emitting diode as follows.

In general, the input signal is a digital signal, and the voltage level of the input signal has two signal levels, high or low. If the input signal is high, a current flows between the base and the emitter of the switching transistor TR, and the switching transistor TR is turned on by the current of the base, so that the current is applied to the light emitting diode LED. As it flows, the light emitting diode (LED) emits light.

At this time, the current flowing through the light emitting diode LED is a power supply voltage applied to the entire circuit, a resistor R2 connected in series with the light emitting diode LED, and a turn-on voltage of the light emitting diode LED. It is determined that the light intensity cannot be controlled, and only the function of turning on or ordering the light emitting diode (LED) is performed.

2 is a driving circuit diagram of a light emitting diode for expressing various conventional colors.

First, in order to produce various colors, a combination of several light emitting diodes (LEDs) must be used, and they are currently used in many devices to express their operating states with various lights.

That is, as shown in FIG. 2, a first light emitting diode LED1 and a first switching transistor TR1 are connected in series between a power supply terminal and a ground terminal, and a second light emitting diode LED2 is connected between the power supply terminal and a ground terminal. And the second switching transistor TR2 are connected in series. Here, the first light emitting diode LED1 and the second light emitting diode LED2 are connected in parallel with each other. In addition, resistors R2 and R4 for supplying a voltage are connected between the power supply terminal and the first and second light emitting diodes LED1 and LED2, respectively, and the bases of the first and second switching transistors TR1 and TR2. Input signals are applied to the resistors R1 and R3, respectively. In this case, the first and second light emitting diodes LED1 and LED2 emit light of different colors, respectively.

FIG. 2 is a driving circuit of a light emitting diode capable of realizing three colors using two input signals.

When a signal applied to the base of the first switching transistor TR1 and the base of the second switching transistor TR2 is named as a first input signal and a second input signal, both the first and second input signals are low. In the case of (Low), there are four cases in which one of the first and second input signals is high, and the first and second input signals are both high.

That is, when both of the first and second input signals are low, the first and second light emitting diodes LED1 and LED2 are all off, so that light does not emit light.

When the first input signal is high and the second input signal is low, only the first light emitting diode LED1 emits light, the first input signal is low, and the second input signal is high. In this state, only the second light emitting diode LED2 emits light.

When the first and second input signals are in a high state, both the first and second light emitting diodes LED1 and LED2 emit light.

Therefore, the number of cases where the first light emitting diode LED1 or the second light emitting diode LED2 is turned on or off, respectively, is four, except that the first and second light emitting diodes LED1 and LED2 are both turned off. Three colors can be expressed. In this case, the first and second light emitting diodes LED1 and LED2 should have different colors, and an LED package including two or three LEDs can be easily obtained on the market. Therefore, the way to get more colors is to use more than two packages of LEDs. If you use a package with three LEDs, you can express seven colors in the structure shown in Figure 2.

Assuming that the first light emitting diode LED1 emits green and the second light emitting diode LED2 emits red, the output colors for the first and second input signals are as follows. Table 1] can be displayed.

First input signal Second input signal Output color low low OFF state Hi low green low Hi Red Hi Hi Yellow or orange

However, such a conventional driving circuit and driving method of a light emitting diode have the following problems.

First, the driving circuit and driving method of the conventional light emitting diode have a limit in expressing many colors.

Second, since the use of light emitting diodes in small devices had only very simple functions, the need for various colors was not high. However, in recent years, many functions have been added to meet the needs of users in small home appliances. As a situation where there are dozens of chords, mobile phones with dozens of chords, enhancement of sound in MP3, colorization of mobile phones, etc., while investing a lot, the simple method of following conventional methods for visual light emitting diodes The situation is merely providing the function.

The present invention has been made to solve the above problems, high density and low-cost full-color light in the small home appliances such as mobile phones or MP3 can be changed freely according to the user's adjustment It is an object of the present invention to provide a driving circuit and a driving method of a light emitting diode.

A driving circuit of a light emitting diode according to the present invention for achieving the above object, the first, second, third and third light emitting diodes emitting red, green, and blue light, and the first, second according to the control signal The first, second and third control current sources for adjusting the current flowing through each of the second and third light emitting diodes, and the respective digital input signals are converted into analog signals to control the first, second and third control current sources. It is characterized by having a first, second, third digital to analog converter for applying a.

In addition, the driving circuit of the light emitting diode according to the present invention for achieving the above object, the first, second, third light emitting diode emitting light of red (R), green (G), blue (B) And amplifying the first, second and third control current sources for adjusting the current applied to the first, second and third light emitting diodes according to the control signal, and the audio signal of the mobile phone with a predetermined gain. It is further characterized by including first, second and third amplifiers for outputting the control signal of the control current source and first, second and third filters for filtering the signals output from the respective amplifiers.

According to an aspect of the present invention, there is provided a method of driving a light emitting diode, the method of driving a light emitting diode having first, second, and third light emitting diodes emitting red, green, and blue light. It is characterized by driving by controlling the current applied to each light emitting diode by modulating the pulse width.

In addition, the driving circuit of the light emitting diode according to the present invention for achieving the above object, the first, second, third light emitting diode emitting light of red (R), green (G), blue (B) In the method of driving a light emitting diode having a, it is another feature to implement a graphic equalizer by amplifying the voice signal of the mobile phone to the first, second, third gain to adjust the current applied to each light emitting diode.

In addition, a driving circuit of a light emitting diode according to the present invention for achieving the above object, the first, each having three light emitting diodes emitting light of red (R), green (G), blue (B), A method of driving a driving circuit of a light emitting diode having a second and a third package, the method comprising: amplifying a voice signal with a first gain, wherein the first package is a red light emitting diode, the second package is a green light emitting diode, The third package controls a current applied to the blue light emitting diode, and amplifies the voice signal with a second gain so that the first package is a green light emitting diode, the second package is a blue light emitting diode, and the third package is a red light. The current applied to the light emitting diode is controlled, and the voice signal is amplified by a third gain so that the first package is a blue light emitting diode and the second package is a red light emitting. A diode, the third package has a further feature in implementing graphic equalizers and controls the current applied to the green light-emitting diode.

The driving circuit and driving method of the LED of the present invention having the above characteristics will be described in more detail with reference to the accompanying drawings.

First, the present invention uses a light emitting diode to linearly adjust the current flowing through the light emitting diodes of three colors (RED, GREEN, BLUE) in a display device such as an electronic display panel or a liquid crystal display device to express thousands or tens of thousands of colors. I would like to use the method. In this case, if the light intensity of each light emitting diode is adjusted by using the colors of light emitting diodes (RED), green (Green), and blue (BLUE), which are three primary colors of light, and adjusting the current flowing through each light emitting diode, The color can be expressed by the cube of the diode's current regulation level. That is, when the number of levels of current flowing through each light emitting diode is 8 (3 bits), 8 * 8 * 8 = 512 colors can be realized.

3 is a driving circuit diagram of a light emitting diode according to a first embodiment of the present invention, and FIG. 4 is a first light emitting diode R, a first control current source CT1 and a first digital-to-analog converter DA1 in FIG. 3. It shows the configuration.

First, second, and third light emitting diodes R, G, and B, which are connected to the power terminals in parallel and emit red, green, and blue light, respectively, and the first, second, and third according to control signals. First, second, and third control current sources CT1, CT2, and CT3 for controlling the current flowing through each of the light emitting diodes R, G, and B, and converting each digital input signal into an analog signal, The first, second, and third digital-to-analog converters DA1, DA2, and DA3 for applying control signals to the second and third control current sources CT1, CT2, and CT3 are provided.

The first, second, and third light emitting diodes R, G, and B may be configured as one package.

The detailed configurations of the control current sources CT1, CT2, and CT3 and the digital / analog converters DA1, DA2, and DA3 are the same as those of FIG. 4.

That is, each control current source is composed of an amplifying transistor TR and a resistor RE, and the digital-to-analog converter is composed of resistors R1 and R2 and a capacitor C1.

The operation of the driving circuit of the light emitting diode will be described below.

The first, second and third digital control signals are input to the inputs of the first, second and third digital-to-analog converters DA1, DA2 and DA3 and the output signals corresponding to the input signals are respectively the first. , And are applied as control signals of the second and third control current sources CT1, CT2, and CT3 to adjust currents flowing through the first, second, and third light emitting diodes R, G, and B, respectively. Therefore, the color of the light summed up from the entire first, second, and third light emitting diodes R, G, and B changes according to the adjusted current.

Here, the driving circuit of the light emitting diode of FIG. 3 shows a basic operation principle, and in many small devices such as mobile phones and MP3s, many digital / analog converters are not built in, so it may be difficult to actually implement the driving circuit. have. Therefore, in this case, another option should be chosen. In general, a small device controlled by a microprocessor provides a general purpose input output (GPIO) pin externally. The present invention intends to provide an example of implementing the driving circuit of the light emitting diode of FIG. 3 using the GPIO pin.

 5 shows an example of a control pulse output from the GPIO pin according to the present invention.

That is, the digital input signal S1 enters the digital signal through the above, and the signal at this time does not always maintain a constant level with time, and as shown in FIG. And Low state become repeated pulse signals. At this time, the pulse signal is varied in duty ratio (a ratio between a high section and a low section) to control the current flowing through the light emitting diode.

In Figure 5, if the input signal is a pulse signal that repeats the high state for a certain time and the low state for a certain time, the average value (V _average ) of the whole signal is as follows.

In order to obtain the above average value, analog (linear) voltages having a constant voltage applied to the base of the amplifying transistor TR may be obtained by using the resistors R1 and R2 and the capacitor C1 having low pass characteristics. Make sure

The voltage at this time, ie, VB, is approximately as follows (where ripple of the signal waveform and base current of the amplifying transistor TR are ignored).

Looking at the above equation, it can be seen that the desired analog output level can be obtained by changing the output level of the digital / analog converter using the input digital signal.

In addition, a signal input to the base of the amplifying transistor TR is converted into an output current by the amplifying transistor TR and the emitter resistor RE. In this case, the output current is as follows.

Here, V _{BE (ON)} is a voltage for turning on the transistor TR.

Therefore, the overall operation of the circuit is to output the input digital signal through the GPIO pin to the pulse width modulation (PWM) signal of the desired light emitting diode signal, the PWM signal through the resistors (R1, R2) and capacitor (C1) Is converted into an analog signal, and the current driving the light emitting diode is adjusted using the amplifying transistor TR and the emitter resistor RE.

Such a circuit may be implemented using various methods, such as operational amplifiers, or other types of current sources may be used instead of the transistor TR.

In addition, the present invention can be used for various applications. That is, in the application of a communication device, when expressing various states such as a communication state, that is, a connection with a network, a type of data service, and an error, it can be represented by various lights.

In addition, in the case of expressing the ringtone of the MP3 or mobile phone, it can be applied to various applications because the height and intensity of the sound can be expressed in a weak color like the graphic equalizer of the audio (Audio).

For example, a graphic equalizer using a voice signal may be implemented.

FIG. 6 illustrates a light emitting diode driving circuit according to a second embodiment of the present invention, and is a driving circuit implementing a graphic equalizer using a ring tone or voice signal of a mobile phone.

That is, the first, second, and third light emitting diodes R, G, and B which emit light of red, green, and blue light, respectively, and the first and second light sources according to control signals. 2, the first, second, third control current sources (CT1, CT2, CT3) for adjusting the current applied to the third light emitting diodes (R, G, B), and the audio signal of the mobile phone, respectively, with a predetermined gain. First, second, and third amplifiers AMP1, AMP2, and AMP3, which are amplified and output as control signals of the respective control current sources, and first, and filters signals output from the respective amplifiers, AMP1, AMP2, and AMP3; It is comprised with the 2nd, 3rd filter (Fiter1, Filter2, Filter3).

FIG. 6 shows an application example in which the light of all light emitting diodes can be adjusted according to music or voice of a mobile phone. The first, second, and third light emitting diodes R, G, and B are packaged in one package. By configuring a number of such packages, and by changing the path of the signal entering each of the first, second, and third light emitting diodes (R, G, B), the effect is as if receiving a large number of input signals can do.

That is, in the first LED package (not shown), the current I1 controlled by the first control current source CT1 is applied to the first LED R, and the second control current source CT2 is included. Current I2 controlled by the second light emitting diode G, and current I3 controlled by the third control current source CT3 are applied to the third light emitting diode B, respectively. In the second LED package (not shown), a current I1 controlled by the first control current source CT1 is applied to the second light emitting diode G by the second control current source CT2. A signal current is changed so that a controlled current I2 is applied to the third light emitting diode B and a current I3 controlled by the third control current source CT3 is applied to the first light emitting diode R, respectively. This will allow for more forms of graphic equalizer.

As described above, the driving circuit and driving method of the LED according to the present invention have the following effects.

First, the present invention is provided with R, G, B light emitting diodes and to adjust the power applied to each light emitting diode can implement a full color in small devices and mobile phones.

Second, the graphic equalizer can be realized by adjusting the gain from the voice signal in the mobile phone.

Third, a full color can be realized by modulating a pulse width of a digital signal input from a small device using a microprocessor through a GPIO pin.

1 is a general light emitting diode driving circuit diagram.

2 is a driving circuit diagram of a light emitting diode for expressing a variety of conventional colors.

3 is a driving circuit diagram of a light emitting diode according to a first embodiment of the present invention;

4 is a detailed configuration diagram of the first light emitting diode R, the first control current source CT1 and the first digital-analog converter DA1 in FIG. 3.

5 is an exemplary diagram of a control pulse output from a GPIO pin in accordance with the present invention.

6 is a light emitting diode driving circuit diagram according to a second embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

CT1, CT2, CT3: control current source R, G, B: light emitting diode

DA1, DA2, DA3: Digital / Analog Converter R1, R2, RE: Resistor

TR: Transistor AM1, AM2, AM3: Amplifier

Claims (9)

First, second, and third light emitting diodes emitting red, green, and blue light, First, second, and third control current sources for adjusting a current flowing through each of the first, second, and third light emitting diodes according to a control signal; And a first, second and third digital to analog converter for converting each digital input signal into an analog signal and applying a control signal to the first, second and third control current sources. LED driving circuit. The method of claim 1, The first, second, and third light emitting diodes of claim 1, wherein the light emitting diode driving circuit of the small device, characterized in that consisting of one package. The method of claim 1, Wherein each control current source comprises an amplifying transistor (TR) and a resistor (RE). The method of claim 1, Wherein each of the digital to analog converters comprises first and second resistors and capacitors. First, second and third light emitting diodes emitting red (R), green (G) and blue (B) light, respectively; First, second and third control current sources for adjusting a current applied to the first, second and third light emitting diodes according to a control signal; First, second and third amplifiers for amplifying a voice signal of a mobile phone with a predetermined gain and outputting the control signal of each control current source; And a first filter, a second filter, and a third filter for filtering signals output from the respective amplifiers. The method of claim 5, A plurality of packages are configured by using the first, second, and third light emitting diodes R, G, and B as one package, and a path of a signal entering each of the first, second, and third light emitting diodes is changed. The LED driving circuit of the small device characterized in that for controlling the current applied to each light emitting diode. In the method of driving a light emitting diode comprising the first, second, and third light emitting diodes emitting red, green, and blue light, And modulating a pulse width to control a current applied to each of the light emitting diodes. In the method of driving a light emitting diode comprising the first, second, and third light emitting diodes emitting red (R), green (G), and blue (B) light, And a graphic equalizer by amplifying a voice signal of a mobile phone with first, second and third gains to adjust a current applied to each of the light emitting diodes. In a driving method of a driving circuit of a light emitting diode having a first, second, and third package having three light emitting diodes emitting red (R), green (G), and blue (B) light, respectively, Amplifying an audio signal with a first gain to control a current applied to the red light emitting diode, the second package to the green light emitting diode, and the third package to the blue light emitting diode, Amplifying the voice signal with a second gain to control a current applied to the green light emitting diode, the second package to the blue light emitting diode, and the third package to the red light emitting diode, By amplifying the voice signal with a third gain, the first package is a blue light emitting diode, the second package is a red light emitting diode, and the third package controls a current applied to the green light emitting diode to implement a graphic equalizer. LED driving method of a small device, characterized in that.