KR101028152B1 - Apparatus for driving Light Emitting Diode - Google Patents

Abstract

According to the present invention, a plurality of LED groups connected to each other, a switching unit for turning on or off the plurality of light emitting diodes, a current sensing unit for sensing currents flowing through the plurality of light emitting diodes, and a plurality of light emitting diodes Provided is a light emitting diode driving apparatus including a current controller for adjusting a size.

LED, liquid crystal display, current

Description

Light-emitting diode driving device {Apparatus for driving Light Emitting Diode}

An embodiment relates to a light emitting diode driving apparatus.

In general, a liquid crystal display device includes two display plates with an electric field applying electrode and a liquid crystal layer having dielectric anisotropy disposed therebetween. A voltage is applied to the field applying electrode to generate an electric field in the liquid crystal layer, and the voltage is changed to adjust the intensity of the electric field to adjust the transmittance of light passing through the liquid crystal layer to display a desired image.

Since the liquid crystal display does not emit light by itself, a separate light source called a backlight is required, and the backlight includes a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), and an external electrode. Fluorescent lamps (EEFL) and the like are used.

The above-described cold cathode fluorescent lamps or external electrode fluorescent lamps consume a lot of power and may deteriorate characteristics of the liquid crystal display due to heat generation. In addition, since the cold cathode fluorescent lamp or the external electrode fluorescent lamp described above is usually manufactured in the form of a rod, it is weak to shock, has a high risk of breakage, and the temperature is not constant according to the lamp position. It may worsen the color reproducibility of the device.

On the other hand, since the light emitting diode is a semiconductor element, it has a long lifetime, fast lighting speed, low power consumption, and excellent color reproducibility. In addition, it is resistant to impact and is advantageous for miniaturization and thinning.

Therefore, backlights using light emitting diodes are being installed in medium and large liquid crystal display devices such as computer monitors and TVs as well as small liquid crystal display devices such as mobile phones.

By the way, such a light emitting diode was able to adjust the pulse width turned on to the light emitting diode by using a pulse width modulation (PWM) signal, but it is impossible to effectively control the brightness of the light emitting diode because the pulse size cannot be controlled. There was a problem.

The LED driving apparatus according to the embodiment can effectively control the brightness of the LED by adjusting the current flowing in the LED.

According to an embodiment, there is provided a light emitting diode driving apparatus including: a light emitting diode group in which a plurality of light emitting diodes are connected; a switching unit for turning on or off a plurality of light emitting diodes; and a current sensing unit sensing current flowing through the plurality of light emitting diodes. And a current controller configured to adjust a magnitude of current flowing through the plurality of light emitting diodes.

The LED driving apparatus according to another embodiment includes a LED group in which a plurality of LEDs are connected, a first switching unit transferring an input voltage by controlling a pulse width modulation signal, and an input voltage transmitted by the first switching unit. A second switching unit which is turned on to turn on the plurality of light emitting diodes, a current sensing unit which senses current flowing through the plurality of light emitting diodes, and a current control unit which adjusts magnitudes of currents flowing through the plurality of light emitting diodes; .

The LED driving apparatus according to the embodiments may not only effectively control the brightness of the LED by controlling the current flowing through the LED, but also provide a stable current for LEDs having various current capacities.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a circuit diagram of a light emitting diode driving apparatus according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a light emitting diode driving apparatus according to a second embodiment of the present invention, and FIG. 3 is a third embodiment of the present invention. 4 is a circuit diagram of the LED driving apparatus according to the present invention, and FIG. 4 is a circuit diagram of the LED driving apparatus according to the fourth embodiment of the present invention.

As shown in FIG. 1, the LED driving apparatus according to the first embodiment of the present invention includes a LED group 1500, a switching unit 1200, a current sensing unit 1300, and a current adjusting unit 1400. Can be configured.

In the group 1500 of the light emitting diodes, a plurality of light emitting diodes L11 and L12 are connected to each other, and the switching unit 1200 turns on or off the plurality of light emitting diodes L11 and L12, and specifically, a bipolar junction transistor. (Bipolar Junction Transistor; BJT) Q12. Here, the resistor R11 is for preventing excessive current from being transmitted when the input voltage Vin is applied to the switching unit 1200.

In addition, the current sensing unit 1300 senses a current Io flowing through the plurality of light emitting diodes L11 and L12, and may be specifically configured as a resistor R12.

On the other hand, the current controller 1400 adjusts the magnitude of the current Io flowing through the plurality of light emitting diodes L11 and L12, and the voltage applied to the base of the bipolar junction transistor Q12 of the switching unit 1200. A voltage difference controller 1410 for controlling a difference in voltage applied to the emitter of the bipolar junction transistor Q12 of the switching unit 1200 and a voltage difference controller 1410 and an amplitude control voltage PAM The amplitude adjusting voltage applying unit 1420 is applied.

Here, the voltage difference adjusting unit 1410 may be configured as a diode D11, and the amplitude adjusting voltage applying unit 1420 may be configured as a resistor R13.

The diode D11 has a difference between the voltage applied to the base of the bipolar junction transistor Q12 of the switching unit 1200 and the voltage applied to the emitter of the bipolar junction transistor Q12 of the switching unit 1200. When the same is selected, when the amplitude adjustment voltage PAM is applied to the amplitude adjustment voltage applying unit 1420 and the bipolar junction transistor Q12 is turned on, the amplitude adjustment voltage PAM is also applied to the current sensing unit 1300. Delivered.

Accordingly, the current Io flowing through the plurality of light emitting diodes L11 and L12 is the same as that of Equation 1 below.

Io = PAM / R12

The LED driving apparatus according to the first exemplary embodiment of the present invention may adjust the currents Io flowing through the plurality of light emitting diodes L11 and L12 when the amplitude adjustment voltage PAM is adjusted.

The LED driving apparatus according to the second embodiment of the present invention will be described with reference to FIG. 2.

As shown in FIG. 2, the LED driving apparatus according to the second embodiment of the present invention includes the LED group 2500, the first switching unit 2100, the second switching unit 2200, and the current sensing unit 2300. And a current controller 2400.

A plurality of light emitting diodes L21 and L22 are connected to the group 2500 of the light emitting diodes, and the first switching unit 2100 transmits an input voltage Vin under the control of the pulse width modulation signal PWM. As a result, a bipolar junction transistor (BJT) Q21 may be formed. Here, the resistor R21 is for preventing excessive current from being transmitted when the input voltage Vin is applied to the first switching unit 2100 or the second switching unit 2200.

In addition, the second switching unit 2200 is turned on by the input voltage Vin transmitted by the first switching unit 2100 to turn on the plurality of light emitting diodes L21 and L22, and specifically, the bipolar junction transistor ( Bipolar Junction Transistor (BJT) (Q22).

In addition, the current sensing unit 1300 senses a current Io flowing through the plurality of light emitting diodes L11 and L12, and may be specifically configured as a resistor R22.

Meanwhile, the current controller 1400 adjusts the magnitude of the current Io flowing through the plurality of light emitting diodes L11 and L12, and the voltage applied to the base of the bipolar junction transistor Q22 of the second switching unit 2200. A voltage difference adjusting unit 2410 for adjusting a difference between voltages applied to the emitter of the bipolar junction transistor Q22 of the switching unit and an amplitude to which the amplitude control voltage PAM is applied, connected to the voltage difference adjusting unit 2410. The control voltage applying unit 2420 is included.

Here, the voltage difference adjusting unit 2410 may be configured as a diode D21, and the amplitude adjusting voltage applying unit 1420 may be configured as a resistor R23.

The diode D21 has an offset voltage applied to a voltage applied to the base of the bipolar junction transistor Q22 of the second switching unit 2200 and an emitter of the bipolar junction transistor Q22 of the second switching unit 2200. When it is selected to be equal to the difference in voltage, when the amplitude adjustment voltage PAM is applied to the amplitude adjustment voltage applying unit 1420 and the bipolar junction transistor Q22 is turned on, the amplitude adjustment voltage PAM is the current sensing unit. It is also passed to (2300).

Therefore, the current Io flowing through the plurality of light emitting diodes L21 and L22 is the same as that of Equation 2.

Io = PAM / R22

The LED driving apparatus according to the second embodiment of the present invention can adjust the currents Io flowing through the plurality of light emitting diodes L21 and L22 when the amplitude adjustment voltage PAM is adjusted. In addition, since the first switching unit 2100 is controlled by the pulse width modulation signal PWM, the duty ratio may be adjusted.

A light emitting diode driving apparatus according to a third embodiment of the present invention will be described with reference to FIG. 3, and a difference from the light emitting diode driving apparatus according to the first embodiment will be described.

The switching unit 3200 of the LED driving apparatus according to the third exemplary embodiment may be configured of a MOS transistor (M32), and the current controller 3400 may include a switching unit 3200. A voltage difference adjusting unit 3410 for adjusting a difference between a voltage applied to the gate of the MOS transistor M32 of the transistor and a voltage applied to a source of the MOS transistor M32 of the switching unit 3200, and a voltage difference adjusting unit ( And an amplitude adjustment voltage applying unit 3420 connected to the 3410 and to which an amplitude adjustment voltage PAM is applied.

The driving device of the LED according to the fourth embodiment of the present invention will be described with reference to FIG. 4, and the difference from the LED driving device according to the second embodiment will be described.

The first switching unit 4100 and the second switching unit 4200 of the LED driving apparatus according to the fourth embodiment may be formed of MOS transistors (MOS FETs) M41 and M42. The current controller 4400 may determine a difference between the voltage applied to the gate of the MOS transistor M42 of the second switching unit 4200 and the voltage applied to the source of the MOS transistor M42 of the second switching unit 4200. A voltage difference adjusting unit 4410 to adjust and an amplitude adjustment voltage applying unit 4420 connected to the voltage difference adjusting unit 4410 and to which an amplitude control voltage PAM is applied.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Rather, those skilled in the art will appreciate that many modifications and variations of the present invention are possible without departing from the spirit and scope of the appended claims.

Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

1 is a circuit diagram of a light emitting diode driving apparatus according to a first embodiment of the present invention.

2 is a circuit diagram of a LED driving apparatus according to a second embodiment of the present invention.

3 is a circuit diagram of a LED driving apparatus according to a third embodiment of the present invention.

4 is a circuit diagram of a LED driving apparatus according to a fourth embodiment of the present invention.

Claims (20)

A light emitting diode group in which a plurality of light emitting diodes are connected; A switching unit including a bipolar junction transistor (BJT) to turn on or turn off the plurality of light emitting diodes; A current sensing unit sensing current flowing through the plurality of light emitting diodes; And A voltage difference controller for controlling a difference between a voltage applied to the base of the bipolar junction transistor of the switching unit and a voltage applied to an emitter of the bipolar junction transistor of the switching unit to adjust the magnitude of the current flowing through the plurality of light emitting diodes; And a current adjusting unit connected to the voltage difference adjusting unit and including an amplitude adjusting voltage applying unit to which an amplitude adjusting voltage is applied. delete delete The method of claim 1, The voltage difference controller includes a diode. The method of claim 1, The amplitude adjusting voltage applying unit includes a resistor. delete A light emitting diode group in which a plurality of light emitting diodes are connected; A switching unit including a metal oxide semiconductor field effect transistor (MOS FET) to turn on or turn off the plurality of light emitting diodes; A current sensing unit sensing current flowing through the plurality of light emitting diodes; And A voltage difference controller for controlling a difference between a voltage applied to a gate of the MOS transistor of the switching unit and a voltage applied to a source of the MOS transistor of the switching unit so as to adjust the magnitudes of currents flowing through the plurality of light emitting diodes; A light emitting diode driving device comprising a current control unit connected to the control unit and including an amplitude control voltage applying unit to which an amplitude control voltage is applied. The method of claim 7, wherein The voltage difference controller includes a diode. The method of claim 7, wherein The amplitude adjusting voltage applying unit includes a resistor. delete delete delete A light emitting diode group in which a plurality of light emitting diodes are connected; A first switching unit including a bipolar junction transistor (BJT) to transfer an input voltage by control of a pulse width modulated signal; A second switching unit including a bipolar junction transistor (BJT) to be turned on by the input voltage delivered by the first switching unit to turn on the plurality of light emitting diodes; A current sensing unit sensing current flowing through the plurality of light emitting diodes; And A voltage difference that adjusts a difference between a voltage applied to the base of the bipolar junction transistor of the second switching unit and a voltage applied to the emitter of the bipolar junction transistor of the second switching unit so as to adjust the magnitude of the current flowing through the plurality of light emitting diodes. And a current adjusting unit connected to the voltage difference adjusting unit and including an amplitude adjusting voltage applying unit to which an amplitude adjusting voltage is applied. The method of claim 13, The voltage difference controller includes a diode. The method of claim 13, The amplitude adjusting voltage applying unit includes a resistor. delete delete A light emitting diode group in which a plurality of light emitting diodes are connected; A first switching unit including a metal oxide semiconductor field effect transistor (MOS FET) to transfer an input voltage by controlling a pulse width modulated signal; A second switching unit including a metal oxide semiconductor field effect transistor (MOS FET) to be turned on by the input voltage delivered by the first switching unit to turn on the plurality of light emitting diodes; A current sensing unit sensing current flowing through the plurality of light emitting diodes; And A voltage difference controller for controlling a difference between a voltage applied to a gate of the MOS transistor of the second switching unit and a voltage applied to a source of the MOS transistor of the second switching unit so as to adjust a magnitude of current flowing through the plurality of light emitting diodes; And a current adjusting unit connected to the voltage difference adjusting unit and including an amplitude adjusting voltage applying unit to which an amplitude adjusting voltage is applied. The method of claim 18, The voltage difference controller includes a diode. The method of claim 18, The amplitude adjusting voltage applying unit includes a resistor.

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