WO2010131889A2 - Light-emitting diode driving circuit and driving method - Google Patents

Light-emitting diode driving circuit and driving method Download PDF

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Publication number
WO2010131889A2
WO2010131889A2 PCT/KR2010/002986 KR2010002986W WO2010131889A2 WO 2010131889 A2 WO2010131889 A2 WO 2010131889A2 KR 2010002986 W KR2010002986 W KR 2010002986W WO 2010131889 A2 WO2010131889 A2 WO 2010131889A2
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Prior art keywords
circuit
light emitting
load transistor
voltage
power supply
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PCT/KR2010/002986
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French (fr)
Korean (ko)
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WO2010131889A3 (en
Inventor
박재현
윤형도
황성민
백광현
서용곤
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전자부품연구원
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Publication of WO2010131889A2 publication Critical patent/WO2010131889A2/en
Publication of WO2010131889A3 publication Critical patent/WO2010131889A3/en

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/347—Dynamic headroom control [DHC]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/375—Switched mode power supply [SMPS] using buck topology
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to a light emitting diode driving circuit and a driving method, and more particularly, to a light emitting diode driving circuit and a driving method that can minimize the waste of power generated in the process of driving the light emitting diode.
  • LEDs Light emitting diodes having a long life, low power consumption, and high efficiency are widely used as lighting means of portable terminals such as mobile communication terminals and PDAs (Personal Digital Assistants).
  • a light emitting diode is a semiconductor device that emits light when a forward voltage is applied.
  • the light output of the light emitting diode is determined by the forward current, and as shown by the current-voltage characteristic curve of the light emitting diode, the change in the forward current is very large due to the small change in the forward voltage. For this reason, the light emitting diode driving circuit requires to keep the desired load current constant at all times, not to control the output voltage.
  • a light emitting diode driving circuit including a constant current source circuit is used to generate a plurality of light emitting diodes with uniform brightness.
  • the constant current source circuit of the conventional LED driving circuit uses a method of feeding back a voltage across a resistor connected in series to the LED in order to control the load current.
  • Such a conventional LED driving circuit uses a resistor in a constant current source circuit, a voltage obtained by adding a voltage drop due to resistance to the forward voltage of a plurality of LEDs is applied to the output voltage.
  • the conventional LED driving circuit further requires power consumed by a resistor in addition to the LED.
  • this resistor since this resistor generally has a tolerance of ⁇ 10% and this is reflected as an error of the output current, there is a problem in that the current deviation of each channel is large when used in multiple channels.
  • the ripple of the output voltage generated in the DC-DC conversion process by the load current sensing value is transferred to the load current as it is, which may cause unwanted optical output ripple or flicker.
  • an object of the present invention is to provide a light emitting diode driving circuit and a driving method capable of minimizing power waste and channel current variation generated in a process of driving a light emitting diode.
  • the present invention uses a constant current source circuit to directly control the forward current of the light emitting diode, and driving the light emitting diode to control the output voltage of the power supply circuit by sensing the voltage applied to the load transistor of the constant current source circuit It provides a circuit and a driving method.
  • the present invention provides a light emitting diode driving circuit comprising a power supply circuit, a constant current source circuit, and an error amplifier.
  • the power supply circuit supplies an output voltage to the plurality of light emitting diodes.
  • the constant current source circuit is configured to control the gate of the load transistor by using a load transistor for driving the plurality of light emitting diodes and a specific bias current value, and the forward drain-source current of the load transistor is a plurality of light emissions as a constant current value. It is driven by input to diode.
  • the error amplifier outputs a voltage value proportional to the difference between the drain-source voltage and the reference voltage of the load transistor.
  • the pulse width modulated signal is generated using the output voltage value of the error amplifier, and the output voltage of the power supply circuit is controlled using the pulse width modulated signal.
  • the error amplifier feeds back the drain-source voltage of the load transistor to the power supply circuit so that the minimum drain-source voltage at which the load transistor can operate in a saturation region is the load.
  • the output voltage of the power supply circuit is controlled to be applied to a transistor.
  • the constant current source circuit controls the light output of the light emitting diode through the control of the specific bias current value.
  • the constant current source circuit may be composed of a current reference circuit or a Darlington circuit, such as various types of current mirror circuits.
  • the power supply circuit includes one of a Boost type, a Buck type, a Buck-Boost type, or an AC-DC SMPS circuit.
  • the Boost type, Buck type, and Buck-Boost type circuits may be DC-DC transformer circuits of a pulse width modulation method.
  • the constant current source circuit includes a plurality of load transistors, and a plurality of light emitting diodes respectively connected to the plurality of load transistors may be connected in parallel.
  • the load transistor may be one of a field effect transistor or a bipolar transistor.
  • the present invention also provides a power supply circuit for supplying an output voltage to a plurality of light emitting diodes, and the constant current source circuit controls the gate of the load transistor using a specific bias current value, thereby controlling the drain-source of the load transistor.
  • the present invention provides a light emitting diode driving method including a control step of generating a pulse width modulated signal using an output voltage value of an amplifier and controlling an output voltage of the power supply circuit using the pulse width modulated signal.
  • the forward current of the light emitting diode inputted from the load transistor is directly controlled through a constant current source circuit such as a current mirror or a Darlington circuit, it is possible to suppress ripple and flicker of the load current.
  • the light emitting diode driving circuit senses the drain-source voltage of the load transistor to control the output voltage of the power supply circuit, thereby minimizing power loss compared to the sensing method using a conventional resistor.
  • the error amplifier feeds back the drain-source voltage of the load transistor to the power supply circuit, thereby controlling the output voltage of the power supply circuit so that the minimum drain-source voltage that the load transistor can operate in the saturation region is applied to the load transistor to emit light.
  • the power loss of the diode driving circuit can be minimized.
  • a constant current source such as a current mirror inside an integrated circuit without using a current sensing resistor, only output current deviations due to mismatches of transistors or asymmetry of semiconductor layout designs occurring in a semiconductor process are obtained.
  • the constant current source circuit can control the light output including on / off of the light emitting diode through the gate control of the load transistor using a specific bias current value, it is possible to control the light output of the light emitting diode. There is no need to provide a separate transistor for the manufacturing cost of the LED driving circuit can be lowered and the design can be simplified.
  • FIG. 1 is a view showing a light emitting diode driving circuit according to the present invention.
  • FIG. 2 is a view showing a light emitting diode driving circuit according to a first embodiment of the present invention.
  • FIG. 3 is a view showing a light emitting diode driving circuit according to a second embodiment of the present invention.
  • FIG. 4 is a view showing a light emitting diode driving circuit according to a third embodiment of the present invention.
  • FIG. 5 is a view showing a light emitting diode driving circuit according to a fourth embodiment of the present invention.
  • the LED driving circuit 100 includes a power supply circuit 10, a constant current source circuit 30, and an error amplifier 40, and includes a constant current source circuit ( 30 directly controls the forward current of the light emitting diode 20.
  • the power supply circuit 10 supplies the output voltage V OUT to the plurality of light emitting diodes 20 connected in series.
  • the constant current source circuit 30 controls the gate of the load transistor Sink Tr by using a load transistor Sink Tr for driving the plurality of light emitting diodes 20 and a specific bias current value I LED .
  • the drain-source current of Sink Tr is input to the plurality of light emitting diodes 20 and driven as a constant current value.
  • the error amplifier 40 receives the drain-source voltage and the reference voltage V REF of the load transistor Sink Tr and outputs a voltage value proportional to the difference, and the output voltage value is the power supply circuit 10. Is input to the pulse width modulator. At this time, the power supply circuit 10 varies the output voltage V OUT according to the control signal of which the output of the error amplifier 40 is pulse width modulated.
  • the LED driving circuit 100 according to the present invention will be described in detail as follows.
  • the power supply circuit 10 supplies an output voltage V OUT to the anodes of the plurality of light emitting diodes 20 connected in series by varying an input voltage V IN applied from the outside.
  • V IN applied from the outside.
  • the power supply circuit 10 includes one of a Boost type, a Buck type, a Buck-Boost type, or an AC-DC SMPS circuit.
  • FIG. 2 shows a Boost type power supply circuit 10a
  • FIG. 3 shows a Buck type power supply circuit 10b
  • the Boost type and Buck type circuits may be DC-DC transformers 12a and 12b controlled by a pulse width modulation (PWM) scheme.
  • PWM pulse width modulation
  • the Buck-Boost type circuit may also be a pulse width modulation DC-DC conversion circuit.
  • the constant current source circuit 30 may be configured as a current reference circuit or a Darlington circuit, such as a current mirror circuit.
  • the constant current source circuit 30 directly controls the forward current of the light emitting diode 20 input from the load transistor Sink Tr and controls the drain-source voltage applied to the load transistor Sink Tr. That is, when the gate of the load transistor Sink Tr is controlled using a specific bias current value I LED , the load transistor Sink Tr inputs a drain-source current to the plurality of light emitting diodes 20 connected in series. That is, the constant current source circuit 30 directly controls the forward current of the light emitting diode 20 by adjusting the specific bias current value I LED .
  • the load transistor Sink Tr may be one of a field effect transistor (FET) or a bipolar junction transistor (BJT).
  • the field effect transistor includes a metal oxide semiconductor (MOS) and a depletion MOS (DMOS), and includes n-type and p-type according to the shape of the constant current source.
  • Bipolar transistors include npn, pnp or Darlington pairs, depending on the type of constant current source.
  • the error amplifier 40 feeds back the drain-source voltage of the load transistor Sink Tr to the power supply circuit 10 so that the minimum drain-source voltage at which the load transistor Sink Tr can operate in a saturation region is the load transistor (
  • the output voltage V OUT of the power supply circuit 10 is controlled to be applied to the sink Tr. That is, the error amplifier 40 senses the drain-source voltage of the load transistor Sink Tr to control the output voltage V OUT of the power supply circuit 10.
  • the constant current source circuit 30 can directly control the light output including the on / off of the light emitting diode 20 by controlling a specific bias current value (I LED ), the light emitting diode 20 It is not necessary to have a separate transistor for controlling the light output of the. At this time, the specific bias current value (I LED ) can be adjusted directly or through pulse width control.
  • the LED driving circuit 100 directly controls the forward current of the LED 20 input from the load transistor Sink Tr through a constant current source circuit 30 such as a current mirror or a Darlington circuit. Therefore, ripple and flicker generation of the load current can be suppressed.
  • the light emitting diode driving circuit 100 senses the drain-source voltage of the load transistor Sink Tr to control the output voltage V OUT of the power supply circuit 10, thereby sensing using a conventional resistor. In comparison, power loss can be minimized.
  • the error amplifier 40 feeds back the drain-source voltage of the load transistor Sink Tr to the power supply circuit 10 so that the minimum drain-source voltage at which the load transistor Sink Tr can operate in a saturation region is loaded.
  • the power loss of the LED driving circuit 100 can be minimized by controlling the output voltage V OUT of the power supply circuit 10 to be applied to the transistor Tink.
  • the constant current source circuit 30 can control the light output including on / off of the light emitting diode 20 by controlling the specific bias current value I LED , the light emitting diode 20 It is not necessary to provide a separate transistor for controlling the light output of the LED can reduce the manufacturing cost of the LED driving circuit 100 and can simplify the design.
  • the light emitting diode driving circuit 100a includes a boost type power supply circuit 10a, as shown in FIG. 2.
  • the power supply circuit 10a is a boosting circuit for boosting the input voltage V IN to an output voltage V OUT required to drive the plurality of light emitting diodes 20.
  • the boost-type DC-DC conversion circuit 12a is provided.
  • a pulse width modulator 14a for controlling the output voltage V OUT of the DC-DC conversion circuit 12a in a pulse width modulation scheme.
  • the DC-DC conversion circuit 12a includes an inductance L 1 , a semiconductor switch D 1 , a capacitor C OUT , and a driving transistor M 1 .
  • the inductance L 1 , the semiconductor switch D 1 , and the capacitor C OUT are connected in series with respect to the input voltage V IN .
  • the driving transistor M 1 is connected in parallel between the inductance L 1 and the semiconductor switch D 1 .
  • the pulse width modulator 14a controls the gate input signal of the driving transistor M 1 in a pulse width modulation scheme to vary the output voltage V OUT output from the DC-DC conversion circuit 12a to provide an optimal load transistor. (Sink Tr) Drain-source voltage is obtained.
  • the LED driving circuit 100a directly controls the forward current of the LED 20 through the constant current source circuit 30 and senses the drain-source voltage of the load transistor Sink Tr.
  • the output voltage V OUT of the power supply circuit 10 is controlled by the pulse width control method.
  • the drain-source voltage of the load transistor Sink Tr depends on the output voltage V OUT of the DC-DC conversion circuit 12a for a specific current value I LED .
  • the output voltage V OUT of the DC-DC conversion circuit 12a is controlled so that the voltage becomes a minimum voltage for driving the constant current source circuit 30. That is, the error amplifier 40 receives the drain-source voltage and the reference voltage V REF of the load transistor Sink Tr, respectively, and applies a voltage value proportional to the difference, and the pulse width modulator 14a of the power supply circuit 10a. Is applied.
  • the pulse width modulator 14a controls the gate input signal of the driving transistor M 1 according to the voltage received from the error amplifier 40 by using a pulse width modulation method to output the output voltage from the DC-DC conversion circuit 12a. Change (V OUT ).
  • the error amplifier 40 feeds back the drain-source voltage of the load transistor Sink Tr to the power supply circuit 10a so that the minimum drain-source voltage at which the load transistor Sink Tr can operate in a saturation region is the load transistor.
  • the output voltage V OUT of the power supply circuit 10a is controlled to be applied to the sink Tr.
  • the light emitting diode driving circuit 100a includes an Boost type power supply circuit 10a, as shown in FIG. 3, the LED driving circuit 100a may include a Buck type power supply circuit 10b. have.
  • the LED driving circuit 100b includes a Buck type power supply circuit 10b.
  • the power supply circuit 10b is a pressure reduction circuit for reducing the input voltage V IN to the output voltage V OUT required to drive the plurality of light emitting diodes 20, and a Buck type DC-DC conversion circuit 12b. And a pulse width modulator 14b for controlling the output voltage V OUT of the DC-DC conversion circuit 12b in a pulse width modulation scheme.
  • the DC-DC conversion circuit 12b includes an inductance L 1 , a semiconductor switch D 1 , a capacitor C OUT , and a driving transistor M 1 .
  • the driving transistor M 1 and the inductance L 1 are connected in series with respect to the input voltage V IN , and the semiconductor switch D 1 is connected in parallel between the driving transistor M 1 and the inductance L 1 . do.
  • the capacitor C OUT is connected between the output terminal of the DC-DC change circuit 12b and the ground voltage.
  • the pulse width modulator 14b controls the gate input signal of the driving transistor M 1 in a pulse width modulation scheme to vary the output voltage V OUT output from the DC-DC conversion circuit 12a to provide an optimal load transistor. (Sink Tr) Drain-source voltage is obtained.
  • the LED driving circuit 100b directly controls the forward current of the LED 20 through the constant current source circuit 30 and senses the drain-source voltage of the load transistor Sink Tr. Since the output voltage V OUT of the power supply circuit 10b is controlled by the pulse width control method, it has the same configuration as that of the first embodiment, and thus the detailed description thereof will be omitted.
  • the light emitting diode driving circuit 100c includes a power supply circuit 10c of the AC-DC SMPS circuit type, as shown in FIG. 4.
  • the light emitting diode driving circuit 100c includes a power supply circuit 10c of the AC-DC SMPS circuit type which outputs AC power as an output voltage V OUT of DC.
  • the power supply circuit 10c includes a rectifier circuit, a transformer, a power semiconductor, and the like.
  • the LED driving circuit 100c directly controls the forward current of the LED 20 through the constant current source circuit 30 and senses the drain-source voltage of the load transistor Sink Tr. Since the output voltage V OUT of the power supply circuit 10b is controlled by the pulse width control method, it has the same configuration as that of the first embodiment, and thus the detailed description thereof will be omitted.
  • one constant current source circuit 30 may include a plurality of load transistors (sink tr. 1, sink tr. 2,..., Sink tr. N).
  • FIG. 5 is a view showing a light emitting diode driving circuit according to a fourth embodiment of the present invention.
  • the light emitting diode driving circuit 100d includes one load transistor (sink tr. 1, sink tr. 2,..., Sink tr. N). And a constant current source circuit 30.
  • a plurality of light emitting diodes 20 are connected to a plurality of load transistors (sink tr.1, sink tr. 2, ..., sink tr. N), respectively, and a plurality of load transistors (sink tr. 1, sink tr. ..., the plurality of light emitting diodes 20 respectively connected to the sink tr.n have a parallel structure again. Since the other structure has the same structure as the light emitting diode driving circuit (100b of FIG. 3) according to the second embodiment, detailed description thereof will be omitted.
  • the light emitting diode driving circuit 100d is a multi-channel driving light emitting diode driving circuit necessary for driving the plurality of light emitting diodes 20 in parallel, and uses one constant current source circuit 30.
  • a plurality of channels are driven by a plurality of load transistors (sink tr.1, sink tr.2, ..., sink tr.n). Therefore, there is no mismatch due to the current sensing resistor, and there is only a deviation of the output current due to mismatch in the semiconductor process of each load transistor (sink tr.1, sink tr.2, ..., sink tr.n). Therefore, the current deviation of each channel can be minimized.
  • the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to aid understanding, and are not intended to limit the scope of the present invention.
  • the lighting circuit using the light emitting diode is exemplified, but may be used in other constant current driving circuits.

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Abstract

The present invention relates to a light-emitting diode driving circuit and driving method for minimizing power waste that occurs when a light-emitting diode is driven using a constant current source and current deviation for each channel during multichannel driving. According to the present invention, a power supply circuit supplies an output voltage to a plurality of light-emitting diodes. A constant current source circuit inputs a drain-source current of a load transistor as a constant current value to a plurality of light-emitting diodes by controlling a gate of the load transistor using a specific bias current value so as to drive the plurality of light-emitting diodes. An error amplifier outputs a voltage value proportional to a difference between a drain-source voltage of the load transistor and a reference voltage. Moreover, a pulse-width modulation signal is generated using an output voltage value of the error amplifier, and an output voltage of the power supply circuit is controlled using the pulse-width modulation signal. At this point, the error amplifier feeds back the drain-source voltage of the load transistor to the power supply circuit in order to control an output voltage of the power supply circuit to enable the minimum drain-source voltage, used for operating the load transistor in a saturation zone, to be applied to the load transistor. Additionally, a plurality of load transistors are connected to one constant current source circuit to drive a plurality of light-emitting diodes connected in parallel, such that a multichannel light-emitting diode driving circuit is achieved to minimize current deviation for each channel.

Description

발광다이오드 구동 회로 및 구동 방법Light emitting diode driving circuit and driving method
본 발명은 발광다이오드 구동 회로 및 구동 방법에 관한 것으로, 더욱 상세하게는 발광다이오드를 구동시키는 과정에서 발생되는 전력 낭비를 최소화할 수 있는 발광다이오드 구동 회로 및 구동 방법에 관한 것이다.The present invention relates to a light emitting diode driving circuit and a driving method, and more particularly, to a light emitting diode driving circuit and a driving method that can minimize the waste of power generated in the process of driving the light emitting diode.
이동통신단말기, PDA(Personal Digital Assistant) 등과 같은 휴대단말기의 조명 수단으로 수명이 길고 전력 소모가 적고 효율이 좋은 발광다이오드(Light Emitting Diode; LED)가 많이 사용되고 있다.BACKGROUND ART Light emitting diodes (LEDs) having a long life, low power consumption, and high efficiency are widely used as lighting means of portable terminals such as mobile communication terminals and PDAs (Personal Digital Assistants).
발광다이오드는 순방향 전압을 인가했을 때 발광하는 반도체 소자이다. 발광다이오드의 광출력은 순방향 전류에 의해 결정되고, 발광다이오드의 전류-전압 특성곡선에서 알 수 있듯이 작은 순방향 전압의 변화에 의해 매우 큰 순방향 전류의 변화를 나타낸다. 이러한 이유로 발광다이오드 구동회로는 출력전압의 제어가 아닌 원하는 부하전류를 항상 일정하게 유지시켜 주는 것을 요구한다.A light emitting diode is a semiconductor device that emits light when a forward voltage is applied. The light output of the light emitting diode is determined by the forward current, and as shown by the current-voltage characteristic curve of the light emitting diode, the change in the forward current is very large due to the small change in the forward voltage. For this reason, the light emitting diode driving circuit requires to keep the desired load current constant at all times, not to control the output voltage.
따라서 복수개의 발광다이오드를 균일한 휘도로 발생시키기 위해서 정전류원 회로를 포함하는 발광다이오드 구동 회로가 사용된다. 종래의 발광다이오드 구동 회로의 정전류원 회로는 부하전류를 제어하기 위해 발광다이오드에 직렬로 연결된 저항에 걸리는 전압을 피드백하는 방식을 사용한다.Therefore, a light emitting diode driving circuit including a constant current source circuit is used to generate a plurality of light emitting diodes with uniform brightness. The constant current source circuit of the conventional LED driving circuit uses a method of feeding back a voltage across a resistor connected in series to the LED in order to control the load current.
이와 같은 종래의 발광다이오드 구동 회로는 정전류원 회로에 저항을 사용하기 때문에, 출력전압으로 복수의 발광다이오드의 순방향 전압에 저항에 의한 전압 강하 분을 더한 전압을 인가해야 한다. 즉 종래의 발광다이오드 구동 회로는 발광다이오드 이외에 저항에 의해 소비되는 전력을 더 필요로 한다. 또한 이 저항이 일반적으로 ±10%의 허용오차를 가지고 이것이 출력 전류의 오차로 반영되기 때문에 다중 채널로 사용할 경우에는 각 채널의 전류 편차가 크게 나는 문제점을 갖는다.Since such a conventional LED driving circuit uses a resistor in a constant current source circuit, a voltage obtained by adding a voltage drop due to resistance to the forward voltage of a plurality of LEDs is applied to the output voltage. In other words, the conventional LED driving circuit further requires power consumed by a resistor in addition to the LED. In addition, since this resistor generally has a tolerance of ± 10% and this is reflected as an error of the output current, there is a problem in that the current deviation of each channel is large when used in multiple channels.
특히 고휘도 발광다이오드를 사용하는 경우, 순방향 전류가 커지게 되고, 이는 저항에 의한 전력 손실도 커지게 된다. 이로 인해 고휘도 발광다이오드를 사용하는 경우 정밀도가 높은 저항을 사용해야 하므로, 고휘도 발광다이오드를 사용하는 제품의 제조 비용을 상승시키는 요인으로 작용한다.In particular, when a high brightness light emitting diode is used, the forward current becomes large, which also causes a large power loss due to the resistance. For this reason, when using a high brightness light emitting diode, a high-precision resistance must be used, which increases the manufacturing cost of a product using the high brightness light emitting diode.
뿐만 아니라 부하전류 센싱값에 의한 DC-DC 변환 과정에서 발생하는 출력전압의 리플(ripple)이 부하전류에 그대로 전달되어 원하는 않는 광출력 리플 또는 플리커(flicker)를 발생시킬 수 있다.In addition, the ripple of the output voltage generated in the DC-DC conversion process by the load current sensing value is transferred to the load current as it is, which may cause unwanted optical output ripple or flicker.
따라서, 본 발명의 목적은 발광다이오드를 구동시키는 과정에서 발생되는 전력 낭비와 채널별 전류 편차를 최소화할 수 있는 발광다이오드 구동 회로 및 구동 방법을 제공하기 위한 것이다.Accordingly, an object of the present invention is to provide a light emitting diode driving circuit and a driving method capable of minimizing power waste and channel current variation generated in a process of driving a light emitting diode.
상기 목적을 달성하기 위하여, 본 발명은 정전류원 회로를 이용하여 발광다이오드의 순방향 전류를 직접 제어하고, 정전류원 회로의 부하 트랜지스터에 걸리는 전압을 센싱하여 전원 공급 회로의 출력전압을 제어하는 발광다이오드 구동 회로 및 구동 방법을 제공한다.In order to achieve the above object, the present invention uses a constant current source circuit to directly control the forward current of the light emitting diode, and driving the light emitting diode to control the output voltage of the power supply circuit by sensing the voltage applied to the load transistor of the constant current source circuit It provides a circuit and a driving method.
본 발명은 전원 공급 회로, 정전류원 회로 및 오차증폭기(error amp)를 포함하여 구성되는 발광다이오드 구동 회로를 제공한다. 상기 전원 공급 회로는 복수의 발광다이오드에 출력전압을 공급한다. 상기 정전류원 회로는 상기 복수의 발광다이오드를 구동시키는 부하 트랜지스터와, 특정 바이어스 전류 값을 이용하여 상기 부하 트랜지스터의 게이트를 제어함으로써 상기 부하 트랜지스터의 순방향의 드레인-소스 전류를 정전류값으로 상기 복수의 발광다이오드에 입력하여 구동시킨다. 그리고 상기 오차증폭기는 상기 부하 트랜지스터의 드레인-소스 전압과 기준 전압의 차이에 비례하는 전압 값을 출력한다. 그리고 상기 오차증폭기의 출력 전압 값을 이용하여 펄스폭 변조 신호를 만들고 이러한 펄스폭 변조 신호를 이용하여 상기 전원 공급 회로의 출력전압을 제어한다. The present invention provides a light emitting diode driving circuit comprising a power supply circuit, a constant current source circuit, and an error amplifier. The power supply circuit supplies an output voltage to the plurality of light emitting diodes. The constant current source circuit is configured to control the gate of the load transistor by using a load transistor for driving the plurality of light emitting diodes and a specific bias current value, and the forward drain-source current of the load transistor is a plurality of light emissions as a constant current value. It is driven by input to diode. The error amplifier outputs a voltage value proportional to the difference between the drain-source voltage and the reference voltage of the load transistor. The pulse width modulated signal is generated using the output voltage value of the error amplifier, and the output voltage of the power supply circuit is controlled using the pulse width modulated signal.
본 발명에 따른 발광다이오드 구동 회로에 있어서, 상기 오차증폭기는 상기 부하 트랜지스터의 드레인-소스 전압을 상기 전원 공급 회로로 피드백시켜 상기 부하 트랜지스터가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 상기 부하 트랜지스터에 인가되도록 상기 전원 공급 회로의 출력전압을 제어한다.In the LED driving circuit according to the present invention, the error amplifier feeds back the drain-source voltage of the load transistor to the power supply circuit so that the minimum drain-source voltage at which the load transistor can operate in a saturation region is the load. The output voltage of the power supply circuit is controlled to be applied to a transistor.
본 발명에 따른 발광다이오드 구동 회로에 있어서, 상기 정전류원 회로는 상기 특정 바이어스 전류값 제어를 통하여 상기 발광다이오드의 광출력을 제어한다.In the light emitting diode driving circuit according to the present invention, the constant current source circuit controls the light output of the light emitting diode through the control of the specific bias current value.
본 발명에 따른 발광다이오드 구동 회로에 있어서, 상기 정전류원 회로는 다양한 형태의 전류거울(current mirror) 회로와 같은 전류 기준회로(current reference) 또는 달링톤(Darlington) 회로로 구성될 수 있다. In the LED driving circuit according to the present invention, the constant current source circuit may be composed of a current reference circuit or a Darlington circuit, such as various types of current mirror circuits.
본 발명에 따른 발광다이오드 구동 회로에 있어서, 상기 전원 공급 회로는 Boost 타입, Buck 타입, Buck-Boost 타입 또는 AC-DC SMPS 회로 중에 하나를 포함한다. 이때 상기 Boost 타입, Buck 타입 및 Buck-Boost 타입 회로는 펄스폭 변조 방식의 DC-DC 변압 회로일 수 있다.In the LED driving circuit according to the present invention, the power supply circuit includes one of a Boost type, a Buck type, a Buck-Boost type, or an AC-DC SMPS circuit. At this time, the Boost type, Buck type, and Buck-Boost type circuits may be DC-DC transformer circuits of a pulse width modulation method.
본 발명에 따른 발광다이오드 구동 회로에 있어서, 상기 정전류원 회로는 복수의 부하 트랜지스터를 포함하며, 상기 복수의 부하 트랜지스터에 각각 연결된 복수의 발광다이오드는 병렬로 연결될 수 있다.In the light emitting diode driving circuit according to the present invention, the constant current source circuit includes a plurality of load transistors, and a plurality of light emitting diodes respectively connected to the plurality of load transistors may be connected in parallel.
본 발명에 따른 발광다이오드 구동 회로에 있어서, 상기 부하 트랜지스터는 전계 효과 트랜지스터 또는 바이폴라 트랜지스터 중에 하나일 수 있다.In the LED driving circuit according to the present invention, the load transistor may be one of a field effect transistor or a bipolar transistor.
본 발명은 또한, 전원 공급 회로는 복수의 발광다이오드에 출력전압을 공급하는 공급 단계와, 상기 정전류원 회로는 특정 바이어스 전류 값을 이용하여 상기 부하 트랜지스터의 게이트를 제어함으로써 상기 부하 트랜지스터의 드레인-소스 전류를 정전류값으로 상기 복수의 발광다이오드에 입력하여 구동시키는 구동 단계와, 상기 오차증폭기는 상기 부하 트랜지스터의 드레인-소스 전압과 기준 전압의 차이에 비례하는 전압 값을 출력하는 출력 단계와, 상기 오차증폭기의 출력 전압 값을 이용하여 펄스폭 변조 신호를 만들고 이러한 펄스폭 변조 신호를 이용하여 상기 전원 공급 회로의 출력전압을 제어하는 제어 단계를 포함하는 발광다이오드 구동 방법을 제공한다.The present invention also provides a power supply circuit for supplying an output voltage to a plurality of light emitting diodes, and the constant current source circuit controls the gate of the load transistor using a specific bias current value, thereby controlling the drain-source of the load transistor. A driving step of driving a current by inputting the current to the plurality of light emitting diodes as a constant current value, the error amplifier outputting a voltage value proportional to a difference between a drain-source voltage and a reference voltage of the load transistor; The present invention provides a light emitting diode driving method including a control step of generating a pulse width modulated signal using an output voltage value of an amplifier and controlling an output voltage of the power supply circuit using the pulse width modulated signal.
본 발명에 따르면, 전류거울 또는 달링톤 회로와 같은 정전류원 회로를 통해 부하 트랜지스터에서 입력되는 발광다이오드의 순방향전류를 직접 제어하기 때문에, 부하 전류의 리플이나 플리커 발생을 억제할 수 있다.According to the present invention, since the forward current of the light emitting diode inputted from the load transistor is directly controlled through a constant current source circuit such as a current mirror or a Darlington circuit, it is possible to suppress ripple and flicker of the load current.
본 발명에 따른 발광다이오드 구동 회로는 부하 트랜지스터의 드레인-소스 전압을 센싱하여 전원 공급 회로의 출력전압을 제어함으로써, 종래의 저항을 이용한 센싱 방법에 비해서 전력 손실을 최소화할 수 있다. 특히 오차증폭기는 부하 트랜지스터의 드레인-소스 전압을 전원 공급 회로로 피드백시킴으로써, 부하 트랜지스터가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 부하 트랜지스터에 인가되도록 전원 공급 회로의 출력전압을 제어하여 발광다이오드 구동 회로의 전력 손실을 최소화할 수 있다. 또한, 전류 센싱 저항을 사용하지 않고 집적회로 내부에서 전류거울과 같은 정전류원을 사용함으로써 반도체 공정에서 발생하는 트랜지스터의 부정합 또는 반도체 배치설계의 비대칭성에 의한 출력 전류 편차만을 가진다. The light emitting diode driving circuit according to the present invention senses the drain-source voltage of the load transistor to control the output voltage of the power supply circuit, thereby minimizing power loss compared to the sensing method using a conventional resistor. In particular, the error amplifier feeds back the drain-source voltage of the load transistor to the power supply circuit, thereby controlling the output voltage of the power supply circuit so that the minimum drain-source voltage that the load transistor can operate in the saturation region is applied to the load transistor to emit light. The power loss of the diode driving circuit can be minimized. In addition, by using a constant current source such as a current mirror inside an integrated circuit without using a current sensing resistor, only output current deviations due to mismatches of transistors or asymmetry of semiconductor layout designs occurring in a semiconductor process are obtained.
그리고 정전류원 회로는 특정 바이어스 전류 값을 이용하여 상기 부하 트랜지스터의 게이트 제어를 통하여 발광다이오드의 온/오프(on/off)를 포함한 광출력을 제어할 수 있기 때문에, 발광다이오드의 광출력을 제어하기 위한 별도의 트랜지스터를 구비할 필요가 없어 발광다이오드 구동 회로의 제조 비용을 낮출 수 있고 설계를 간소화할 수 있다.In addition, since the constant current source circuit can control the light output including on / off of the light emitting diode through the gate control of the load transistor using a specific bias current value, it is possible to control the light output of the light emitting diode. There is no need to provide a separate transistor for the manufacturing cost of the LED driving circuit can be lowered and the design can be simplified.
도 1은 본 발명에 따른 발광다이오드 구동 회로를 보여주는 도면이다.1 is a view showing a light emitting diode driving circuit according to the present invention.
도 2는 본 발명의 제1 실시예에 따른 발광다이오드 구동 회로를 보여주는 도면이다.2 is a view showing a light emitting diode driving circuit according to a first embodiment of the present invention.
도 3은 본 발명의 제2 실시예에 따른 발광다이오드 구동 회로를 보여주는 도면이다.3 is a view showing a light emitting diode driving circuit according to a second embodiment of the present invention.
도 4는 본 발명의 제3 실시예에 따른 발광다이오드 구동 회로를 보여주는 도면이다.4 is a view showing a light emitting diode driving circuit according to a third embodiment of the present invention.
도 5는 본 발명의 제4 실시예에 따른 발광다이오드 구동 회로를 보여주는 도면이다.5 is a view showing a light emitting diode driving circuit according to a fourth embodiment of the present invention.
이하, 첨부 도면을 참조하여 본 발명의 실시예를 보다 상세하게 설명하고자 한다.Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.
본 발명에 따른 발광다이오드 구동 회로(100)는, 도 1에 도시된 바와 같이, 전원 공급 회로(10), 정전류원 회로(30) 및 오차증폭기(40)를 포함하여 구성되며, 정전류원 회로(30)를 통해 발광다이오드(20)의 순방향전류를 직접 제어한다. 전원 공급 회로(10)는 직렬로 연결된 복수의 발광다이오드(20)에 출력전압(VOUT)을 공급한다. 정전류원 회로(30)는 복수의 발광다이오드(20)를 구동시키는 부하 트랜지스터(Sink Tr)와, 특정 바이어스 전류값(ILED)을 이용하여 부하 트랜지스터(Sink Tr)의 게이트를 제어하여 부하 트랜지스터(Sink Tr)의 드레인-소스 전류를 정전류값으로 복수의 발광다이오드(20)에 입력하여 구동시킨다. 그리고 오차증폭기(40)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압과 기준 전압(VREF)을 각각 입력받아 그 차이에 비례하는 전압 값을 출력하고, 이 출력 전압 값은 전원 공급 회로(10)의 펄스폭 변조기로 입력된다. 이때 전원 공급 회로(10)는 오차증폭기(40)의 출력이 펄스폭 변조된 제어신호에 따라 출력전압(VOUT)을 가변시킨다.As shown in FIG. 1, the LED driving circuit 100 according to the present invention includes a power supply circuit 10, a constant current source circuit 30, and an error amplifier 40, and includes a constant current source circuit ( 30 directly controls the forward current of the light emitting diode 20. The power supply circuit 10 supplies the output voltage V OUT to the plurality of light emitting diodes 20 connected in series. The constant current source circuit 30 controls the gate of the load transistor Sink Tr by using a load transistor Sink Tr for driving the plurality of light emitting diodes 20 and a specific bias current value I LED . The drain-source current of Sink Tr is input to the plurality of light emitting diodes 20 and driven as a constant current value. The error amplifier 40 receives the drain-source voltage and the reference voltage V REF of the load transistor Sink Tr and outputs a voltage value proportional to the difference, and the output voltage value is the power supply circuit 10. Is input to the pulse width modulator. At this time, the power supply circuit 10 varies the output voltage V OUT according to the control signal of which the output of the error amplifier 40 is pulse width modulated.
본 발명에 따른 발광다이오드 구동 회로(100)에 대해서 구체적으로 설명하면 다음과 같다.The LED driving circuit 100 according to the present invention will be described in detail as follows.
전원 공급 회로(10)는 외부에서 인가되는 입력전압(VIN)을 가변하여 출력전압(VOUT)을 직렬 연결된 복수의 발광다이오드(20)의 양극으로 공급한다. 이때 도 1에서는 복수의 발광다이오드(20)가 직렬로 연결된 예를 개시하였지만 이에 한정되는 것은 아니다. 즉 복수의 발광다이오드(20)는 병렬로 연결되거나, 직렬과 병렬이 혼합된 형태로 연결될 수도 있다. 예컨대 전원 공급 회로(10)는 Boost 타입, Buck 타입, Buck-Boost 타입 또는 AC-DC SMPS 회로 중에 하나를 포함한다. 도 2는 Boost 타입의 전원 공급 회로(10a)를 도시하고 있고, 도 3은 Buck 타입의 전원 공급 회로(10b)를 도시하고 있고, 도 4는 AC-DC SMPS 회로의 전원 공급 회로(10c)를 도시하고 있다. 도 2 및 도 3에 도시된 바와 같이, Boost 타입 및 Buck 타입 회로는 펄스폭 변조(Pulse Width Modulation; PWM) 방식에 의해 제어되는 DC-DC 변압 회로(12a,12b)일 수 있다. 물론 Buck-Boost 타입 회로 또한 펄스폭 변조 방식의 DC-DC 변환 회로일 수 있다.The power supply circuit 10 supplies an output voltage V OUT to the anodes of the plurality of light emitting diodes 20 connected in series by varying an input voltage V IN applied from the outside. 1 illustrates an example in which a plurality of light emitting diodes 20 are connected in series, but is not limited thereto. That is, the plurality of light emitting diodes 20 may be connected in parallel or may be connected in a form of a mixture of serial and parallel. For example, the power supply circuit 10 includes one of a Boost type, a Buck type, a Buck-Boost type, or an AC-DC SMPS circuit. FIG. 2 shows a Boost type power supply circuit 10a, FIG. 3 shows a Buck type power supply circuit 10b, and FIG. 4 shows a power supply circuit 10c of an AC-DC SMPS circuit. It is shown. 2 and 3, the Boost type and Buck type circuits may be DC- DC transformers 12a and 12b controlled by a pulse width modulation (PWM) scheme. Of course, the Buck-Boost type circuit may also be a pulse width modulation DC-DC conversion circuit.
정전류원 회로(30)는 전류거울(current mirror) 회로와 같은 전류 기준회로(current reference) 또는 달링톤(Darlington) 회로로 구성될 수 있다. 정전류원 회로(30)는 부하 트랜지스터(Sink Tr)에서 입력되는 발광다이오드(20)의 순방향 전류를 직접 제어하고 부하 트랜지스터(Sink Tr)에 걸리는 드레인-소스 전압을 제어한다. 즉 특정 바이어스 전류값(ILED)을 이용하여 부하 트랜지스터(Sink Tr)의 게이트를 제어하면, 부하 트랜지스터(Sink Tr)는 드레인-소스 전류를 직렬 연결된 복수의 발광다이오드(20)에 입력한다. 즉 정전류원 회로(30)는 특정 바이어스 전류값(ILED)의 조절을 통하여 발광다이오드(20)의 순방향 전류를 직접 제어한다.The constant current source circuit 30 may be configured as a current reference circuit or a Darlington circuit, such as a current mirror circuit. The constant current source circuit 30 directly controls the forward current of the light emitting diode 20 input from the load transistor Sink Tr and controls the drain-source voltage applied to the load transistor Sink Tr. That is, when the gate of the load transistor Sink Tr is controlled using a specific bias current value I LED , the load transistor Sink Tr inputs a drain-source current to the plurality of light emitting diodes 20 connected in series. That is, the constant current source circuit 30 directly controls the forward current of the light emitting diode 20 by adjusting the specific bias current value I LED .
이때 부하 트랜지스터(Sink Tr)는 전계 효과 트랜지스터(Field Effect Transistor; FET) 또는 바이폴라 트랜지스터(Bipolar Junction Transistor; BJT) 중에 하나일 수 있다. 전계 효과 트랜지스터는 MOS(Metal Oxide Semiconductor)와 DMOS(Depletion MOS)를 포함하며, 정전류원의 형태에 따라 n-type과 p-type을 포함한다. 바이폴라 트랜지스터는 정전류원의 형태에 따라 npn, pnp 또는 Darlington pair를 포함한다. 부하 트랜지스터(Sink Tr)로 바이폴라 트랜지스터를 사용하는 경우 콜렉터-에미터 전압을 센싱하고 이 값을 최적화시킨다.In this case, the load transistor Sink Tr may be one of a field effect transistor (FET) or a bipolar junction transistor (BJT). The field effect transistor includes a metal oxide semiconductor (MOS) and a depletion MOS (DMOS), and includes n-type and p-type according to the shape of the constant current source. Bipolar transistors include npn, pnp or Darlington pairs, depending on the type of constant current source. When using a bipolar transistor as the load transistor (Sink Tr), the collector-emitter voltage is sensed and optimized.
오차증폭기(40)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 전원 공급 회로(10)로 피드백시켜 부하 트랜지스터(Sink Tr)가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 부하 트랜지스터(Sink Tr)에 인가되도록 전원 공급 회로(10)의 출력전압(VOUT)을 제어한다. 즉 오차증폭기(40)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 센싱하여 전원 공급 회로(10)의 출력전압(VOUT)을 제어한다.The error amplifier 40 feeds back the drain-source voltage of the load transistor Sink Tr to the power supply circuit 10 so that the minimum drain-source voltage at which the load transistor Sink Tr can operate in a saturation region is the load transistor ( The output voltage V OUT of the power supply circuit 10 is controlled to be applied to the sink Tr. That is, the error amplifier 40 senses the drain-source voltage of the load transistor Sink Tr to control the output voltage V OUT of the power supply circuit 10.
그리고 정전류원 회로(30)는 특정 바이어스 전류값(ILED) 제어를 통하여 발광다이오드(20)의 온/오프(on/off)를 포함한 광출력을 직접 제어할 수 있기 때문에, 발광다이오드(20)의 광출력을 제어하기 위한 별도의 트랜지스터를 구비할 필요가 없다. 이때 특정 바이어스 전류값(ILED)은 직접 조절하거나 펄스폭 제어를 통해 조절할 수 있다.In addition, since the constant current source circuit 30 can directly control the light output including the on / off of the light emitting diode 20 by controlling a specific bias current value (I LED ), the light emitting diode 20 It is not necessary to have a separate transistor for controlling the light output of the. At this time, the specific bias current value (I LED ) can be adjusted directly or through pulse width control.
이와 같이 본 발명에 따른 발광다이오드 구동 회로(100)는 전류거울 또는 달링톤 회로와 같은 정전류원 회로(30)를 통해 부하 트랜지스터(Sink Tr)에서 입력되는 발광다이오드(20)의 순방향전류를 직접 제어하기 때문에, 부하 전류의 리플이나 플리커 발생을 억제할 수 있다.As such, the LED driving circuit 100 according to the present invention directly controls the forward current of the LED 20 input from the load transistor Sink Tr through a constant current source circuit 30 such as a current mirror or a Darlington circuit. Therefore, ripple and flicker generation of the load current can be suppressed.
본 발명에 따른 발광다이오드 구동 회로(100)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 센싱하여 전원 공급 회로(10)의 출력전압(VOUT)을 제어함으로써, 종래의 저항을 이용한 센싱 방법에 비해서 전력 손실을 최소화할 수 있다. 특히 오차증폭기(40)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 전원 공급 회로(10)로 피드백시킴으로써, 부하 트랜지스터(Sink Tr)가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 부하 트랜지스터(Sink Tr)에 인가되도록 전원 공급 회로(10)의 출력전압(VOUT)을 제어하여 발광다이오드 구동 회로(100)의 전력 손실을 최소화할 수 있다. 또한, 다중 채널 응용을 함에 있어서, 하나의 정전류원 회로(30)에 대해 복수의 부하 트랜지스터(Sink Tr)를 연결하는 방법으로 구성을 하기 때문에 각 채널별 전류편차를 부하 트랜지스터(Sink Tr)의 반도체 공정상의 부정합 정도로 줄일 수 있다.The light emitting diode driving circuit 100 according to the present invention senses the drain-source voltage of the load transistor Sink Tr to control the output voltage V OUT of the power supply circuit 10, thereby sensing using a conventional resistor. In comparison, power loss can be minimized. In particular, the error amplifier 40 feeds back the drain-source voltage of the load transistor Sink Tr to the power supply circuit 10 so that the minimum drain-source voltage at which the load transistor Sink Tr can operate in a saturation region is loaded. The power loss of the LED driving circuit 100 can be minimized by controlling the output voltage V OUT of the power supply circuit 10 to be applied to the transistor Tink. In addition, in a multi-channel application, since a plurality of load transistors (Sink Tr) are connected to one constant current source circuit 30, the current deviation of each channel is determined by the semiconductor of the load transistor (Sink Tr). The degree of mismatch in the process can be reduced.
그리고 정전류원 회로(30)는 특정 바이어스 전류값(ILED)의 제어를 통하여 발광다이오드(20)의 온/오프(on/off)를 포함한 광출력을 제어할 수 있기 때문에, 발광다이오드(20)의 광출력을 제어하기 위한 별도의 트랜지스터를 구비할 필요가 없어 발광다이오드 구동 회로(100)의 제조 비용을 낮출 수 있고 설계를 간소화할 수 있다.In addition, since the constant current source circuit 30 can control the light output including on / off of the light emitting diode 20 by controlling the specific bias current value I LED , the light emitting diode 20 It is not necessary to provide a separate transistor for controlling the light output of the LED can reduce the manufacturing cost of the LED driving circuit 100 and can simplify the design.
제1 실시예First embodiment
본 발명의 제1 실시예에 따른 발광다이오드 구동 회로(100a)는, 도 2에 도시된 바와 같이, Boost 타입의 전원 공급 회로(10a)를 포함한다.The light emitting diode driving circuit 100a according to the first embodiment of the present invention includes a boost type power supply circuit 10a, as shown in FIG. 2.
전원 공급 회로(10a)는 입력 전압(VIN)을 복수의 발광다이오드(20)를 구동시키는 데 필요한 출력전압(VOUT)으로 승압시키는 승압 회로로서, Boost 타입의 DC-DC 변환 회로(12a)와, DC-DC 변환 회로(12a)의 출력전압(VOUT)을 펄스폭 변조 방식으로 제어하는 펄스폭 변조기(14a)를 포함한다.The power supply circuit 10a is a boosting circuit for boosting the input voltage V IN to an output voltage V OUT required to drive the plurality of light emitting diodes 20. The boost-type DC-DC conversion circuit 12a is provided. And a pulse width modulator 14a for controlling the output voltage V OUT of the DC-DC conversion circuit 12a in a pulse width modulation scheme.
DC-DC 변환 회로(12a)는 인덕턴스(L1), 반도체 스위치(D1), 콘덴서(COUT) 및 구동 트랜지스터(M1)를 포함한다. 입력전압(VIN)에 대해 인덕턴스(L1), 반도체 스위치(D1) 및 콘덴서(COUT)가 직렬로 연결된다. 구동 트랜지스터(M1)는 인덕턴스(L1)와 반도체 스위치(D1) 사이에 병렬로 연결된다.The DC-DC conversion circuit 12a includes an inductance L 1 , a semiconductor switch D 1 , a capacitor C OUT , and a driving transistor M 1 . The inductance L 1 , the semiconductor switch D 1 , and the capacitor C OUT are connected in series with respect to the input voltage V IN . The driving transistor M 1 is connected in parallel between the inductance L 1 and the semiconductor switch D 1 .
그리고 펄스폭 변조기(14a)는 구동 트랜지스터(M1)의 게이트 입력 신호를 펄스폭 변조 방식으로 제어하여 DC-DC 변환 회로(12a)에서 출력되는 출력전압(VOUT)을 가변시켜 최적의 부하 트랜지스터(Sink Tr) 드레인-소스 전압을 얻는다.In addition, the pulse width modulator 14a controls the gate input signal of the driving transistor M 1 in a pulse width modulation scheme to vary the output voltage V OUT output from the DC-DC conversion circuit 12a to provide an optimal load transistor. (Sink Tr) Drain-source voltage is obtained.
이와 같은 제1 실시예에 따른 발광다이오드 구동 회로(100a)는 정전류원 회로(30)를 통해 발광다이오드(20)의 순방향전류를 직접 제어하고, 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 센싱하여 전원 공급 회로(10)의 출력전압(VOUT)을 펄스폭 제어 방식으로 제어한다.The LED driving circuit 100a according to the first embodiment directly controls the forward current of the LED 20 through the constant current source circuit 30 and senses the drain-source voltage of the load transistor Sink Tr. The output voltage V OUT of the power supply circuit 10 is controlled by the pulse width control method.
구체적으로 설명하면, 부하 트랜지스터(Sink Tr)의 드레인-소스 전압은 특정 전류값(ILED)에 대해 DC-DC 변환 회로(12a)의 출력전압(VOUT)에 따라 달라지게 되는데, 드레인-소스 전압이 정전류원 회로(30)를 구동하기 위한 최소 전압이 되도록 DC-DC 변환 회로(12a)의 출력전압(VOUT)을 제어한다. 즉 오차증폭기(40)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압과 기준 전압(VREF)을 각각 입력받아 그 차이에 비례하는 전압 값을 전원 공급 회로(10a)의 펄스폭 변조기(14a)로 인가한다. 그리고 펄스폭 변조기(14a)는 오차증폭기(40)로부터 입력받은 전압에 따라 구동 트랜지스터(M1)의 게이트 입력 신호를 펄스폭 변조 방식으로 제어하여 DC-DC 변환 회로(12a)에서 출력되는 출력전압(VOUT)을 가변시킨다. 이때 오차증폭기(40)는 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 전원 공급 회로(10a)로 피드백시켜 부하 트랜지스터(Sink Tr)가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 부하 트랜지스터(Sink Tr)에 인가되도록 전원 공급 회로(10a)의 출력전압(VOUT)을 제어한다.Specifically, the drain-source voltage of the load transistor Sink Tr depends on the output voltage V OUT of the DC-DC conversion circuit 12a for a specific current value I LED . The output voltage V OUT of the DC-DC conversion circuit 12a is controlled so that the voltage becomes a minimum voltage for driving the constant current source circuit 30. That is, the error amplifier 40 receives the drain-source voltage and the reference voltage V REF of the load transistor Sink Tr, respectively, and applies a voltage value proportional to the difference, and the pulse width modulator 14a of the power supply circuit 10a. Is applied. In addition, the pulse width modulator 14a controls the gate input signal of the driving transistor M 1 according to the voltage received from the error amplifier 40 by using a pulse width modulation method to output the output voltage from the DC-DC conversion circuit 12a. Change (V OUT ). The error amplifier 40 feeds back the drain-source voltage of the load transistor Sink Tr to the power supply circuit 10a so that the minimum drain-source voltage at which the load transistor Sink Tr can operate in a saturation region is the load transistor. The output voltage V OUT of the power supply circuit 10a is controlled to be applied to the sink Tr.
제2 실시예Second embodiment
제1 실시예에 따른 발광다이오드 구동 회로(100a)는 Boost 타입의 전원 공급 회로(10a)를 포함하는 예시하였지만, 도 3에 도시된 바와 같이, Buck 타입의 전원 공급 회로(10b)를 포함할 수 있다.Although the light emitting diode driving circuit 100a according to the first embodiment includes an Boost type power supply circuit 10a, as shown in FIG. 3, the LED driving circuit 100a may include a Buck type power supply circuit 10b. have.
도 3을 참조하면, 본 발명의 제2 실시예에 따른 발광다이오드 구동 회로(100b)는 Buck 타입의 전원 공급 회로(10b)를 포함한다.Referring to FIG. 3, the LED driving circuit 100b according to the second embodiment of the present invention includes a Buck type power supply circuit 10b.
전원 공급 회로(10b)는 입력전압(VIN)을 복수의 발광다이오드(20)를 구동시키는 데 필요한 출력전압(VOUT)으로 감압시키는 감압 회로로서, Buck 타입의 DC-DC 변환 회로(12b)와, DC-DC 변환 회로(12b)의 출력전압(VOUT)을 펄스폭 변조 방식으로 제어하는 펄스폭 변조기(14b)를 포함한다.The power supply circuit 10b is a pressure reduction circuit for reducing the input voltage V IN to the output voltage V OUT required to drive the plurality of light emitting diodes 20, and a Buck type DC-DC conversion circuit 12b. And a pulse width modulator 14b for controlling the output voltage V OUT of the DC-DC conversion circuit 12b in a pulse width modulation scheme.
DC-DC 변환 회로(12b)는 인덕턴스(L1), 반도체 스위치(D1), 콘덴서(COUT) 및 구동 트랜지스터(M1)를 포함한다. 입력전압(VIN)에 대해 구동 트랜지스터(M1)와 인덕턴스(L1)가 직렬로 연결되고, 구동 트랜지스터(M1)와 인덕턴스(L1) 사이에 병렬로 반도체 스위치(D1)가 연결된다. 콘덴서(COUT)는 DC-DC 변화 회로(12b)의 출력단과 접지 전압 사이에 연결된다.The DC-DC conversion circuit 12b includes an inductance L 1 , a semiconductor switch D 1 , a capacitor C OUT , and a driving transistor M 1 . The driving transistor M 1 and the inductance L 1 are connected in series with respect to the input voltage V IN , and the semiconductor switch D 1 is connected in parallel between the driving transistor M 1 and the inductance L 1 . do. The capacitor C OUT is connected between the output terminal of the DC-DC change circuit 12b and the ground voltage.
그리고 펄스폭 변조기(14b)는 구동 트랜지스터(M1)의 게이트 입력 신호를 펄스폭 변조 방식으로 제어하여 DC-DC 변환 회로(12a)에서 출력되는 출력전압(VOUT)을 가변시켜 최적의 부하 트랜지스터(Sink Tr) 드레인-소스 전압을 얻는다.In addition, the pulse width modulator 14b controls the gate input signal of the driving transistor M 1 in a pulse width modulation scheme to vary the output voltage V OUT output from the DC-DC conversion circuit 12a to provide an optimal load transistor. (Sink Tr) Drain-source voltage is obtained.
이와 같은 제2 실시예에 따른 발광다이오드 구동 회로(100b)는 정전류원 회로(30)를 통해 발광다이오드(20)의 순방향전류를 직접 제어하고, 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 센싱하여 전원 공급 회로(10b)의 출력전압(VOUT)을 펄스폭 제어 방식으로 제어한다는 점에서 제1 실시예와 동일한 구성을 갖기 때문에 상세한 설명은 생략한다.The LED driving circuit 100b according to the second embodiment directly controls the forward current of the LED 20 through the constant current source circuit 30 and senses the drain-source voltage of the load transistor Sink Tr. Since the output voltage V OUT of the power supply circuit 10b is controlled by the pulse width control method, it has the same configuration as that of the first embodiment, and thus the detailed description thereof will be omitted.
제3 실시예Third embodiment
그리고 본 발명의 제3 실시예에 따른 발광다이오드 구동 회로(100c)는, 도 4에 도시된 바와 같이, AC-DC SMPS 회로 타입의 전원 공급 회로(10c)를 포함한다.The light emitting diode driving circuit 100c according to the third embodiment of the present invention includes a power supply circuit 10c of the AC-DC SMPS circuit type, as shown in FIG. 4.
제3 실시예에 따른 발광다이오드 구동 회로(100c)는 AC 전원을 DC의 출력전압(VOUT)으로 출력하는 AC-DC SMPS 회로 타입의 전원 공급 회로(10c)를 포함한다. 전원 공급 회로(10c)는 정류회로, 변압기 및 전력반도체 등을 포함한다.The light emitting diode driving circuit 100c according to the third embodiment includes a power supply circuit 10c of the AC-DC SMPS circuit type which outputs AC power as an output voltage V OUT of DC. The power supply circuit 10c includes a rectifier circuit, a transformer, a power semiconductor, and the like.
이와 같은 제3 실시예에 따른 발광다이오드 구동 회로(100c)는 정전류원 회로(30)를 통해 발광다이오드(20)의 순방향전류를 직접 제어하고, 부하 트랜지스터(Sink Tr)의 드레인-소스 전압을 센싱하여 전원 공급 회로(10b)의 출력전압(VOUT)을 펄스폭 제어 방식으로 제어한다는 점에서 제1 실시예와 동일한 구성을 갖기 때문에 상세한 설명은 생략한다.The LED driving circuit 100c according to the third exemplary embodiment directly controls the forward current of the LED 20 through the constant current source circuit 30 and senses the drain-source voltage of the load transistor Sink Tr. Since the output voltage V OUT of the power supply circuit 10b is controlled by the pulse width control method, it has the same configuration as that of the first embodiment, and thus the detailed description thereof will be omitted.
제4 실시예Fourth embodiment
한편 제1 내지 제3 실시예에 다른 발광다이오드 구동 회로는 하나의 정전류원 회로는 하나의 부하 트랜지스터를 포함하는 예를 개시하였지만 이것에 한정되는 것은 아니다. 예컨대 도 5에 도시된 바와 같이, 하나의 정전류원 회로(30)는 복수의 부하 트랜지스터(sink tr.1, sink tr.2, …, sink tr.n)를 포함할 수 있다.On the other hand, in the light emitting diode driving circuit according to the first to third embodiments, an example in which one constant current source circuit includes one load transistor is disclosed, but the present invention is not limited thereto. For example, as shown in FIG. 5, one constant current source circuit 30 may include a plurality of load transistors (sink tr. 1, sink tr. 2,..., Sink tr. N).
도 5는 본 발명의 제4 실시예에 따른 발광다이오드 구동 회로를 보여주는 도면이다.5 is a view showing a light emitting diode driving circuit according to a fourth embodiment of the present invention.
도 5를 참조하면, 본 발명의 제4 실시예에 따른 발광다이오드 구동 회로(100d)는, 복수의 부하 트랜지스터(sink tr.1, sink tr.2, …, sink tr.n)를 갖는 하나의 정전류원 회로(30)를 포함한다. 복수의 부하 트랜지스터(sink tr.1, sink tr.2, …, sink tr.n)에 각각 복수의 발광다이오드(20)가 연결되며, 복수의 부하 트랜지스터(sink tr.1, sink tr.2, …, sink tr.n)에 각각 연결된 복수의 발광다이오드(20)는 다시 병렬된 구조를 갖는다. 그 외 구조는 제2 실시예에 따른 발광다이오드 구동 회로(도 3의 100b)와 동일한 구조를 갖기 때문에 상세한 설명은 생략한다.Referring to FIG. 5, the light emitting diode driving circuit 100d according to the fourth embodiment of the present invention includes one load transistor (sink tr. 1, sink tr. 2,..., Sink tr. N). And a constant current source circuit 30. A plurality of light emitting diodes 20 are connected to a plurality of load transistors (sink tr.1, sink tr. 2, ..., sink tr. N), respectively, and a plurality of load transistors (sink tr. 1, sink tr. ..., the plurality of light emitting diodes 20 respectively connected to the sink tr.n have a parallel structure again. Since the other structure has the same structure as the light emitting diode driving circuit (100b of FIG. 3) according to the second embodiment, detailed description thereof will be omitted.
이와 같이 제4 실시예에 따른 발광다이오드 구동 회로(100d)는 복수의 발광다이오드(20)를 병렬로 구동하기 위해 필요한 다중 채널 구동 발광다이오드 구동 회로로서, 하나의 정전류원 회로(30)를 이용하여 복수의 부하 트랜지스터(sink tr.1, sink tr.2, …, sink tr.n)로 다수의 채널을 구동하는 방법이다. 따라서, 전류 센싱 저항에 의한 부정합은 없음으로 오직 각 부하 트랜지스터(sink tr.1, sink tr.2, …, sink tr.n)가 갖는 반도체 공정상의 부정합으로 인한 출력 전류의 편차만이 존재하기 때문에, 각 채널별 전류 편차를 최소화 할 수 있다.As described above, the light emitting diode driving circuit 100d according to the fourth embodiment is a multi-channel driving light emitting diode driving circuit necessary for driving the plurality of light emitting diodes 20 in parallel, and uses one constant current source circuit 30. A plurality of channels are driven by a plurality of load transistors (sink tr.1, sink tr.2, ..., sink tr.n). Therefore, there is no mismatch due to the current sensing resistor, and there is only a deviation of the output current due to mismatch in the semiconductor process of each load transistor (sink tr.1, sink tr.2, ..., sink tr.n). Therefore, the current deviation of each channel can be minimized.
한편, 본 명세서와 도면에 개시된 본 발명의 실시예들은 이해를 돕기 위해 특정 예를 제시한 것에 지나지 않으며, 본 발명의 범위를 한정하고자 하는 것은 아니다. 여기에 개시된 실시예들 이외에도 본 발명의 기술적 사상에 바탕을 둔 다른 변형예들이 실시 가능하다는 것은, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에게 자명한 것이다. 한편 본 실시예에서는 발광다이오드를 이용한 조명 회로를 예시하였지만 다른 정전류 구동회로에도 사용될 수 있다.On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to aid understanding, and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is apparent to those skilled in the art that other modifications based on the technical idea of the present invention may be implemented. In the present embodiment, the lighting circuit using the light emitting diode is exemplified, but may be used in other constant current driving circuits.

Claims (13)

  1. 복수의 발광다이오드에 출력전압을 공급하는 전원 공급 회로;A power supply circuit for supplying output voltages to the plurality of light emitting diodes;
    상기 복수의 발광다이오드를 구동시키는 부하 트랜지스터와, 특정 바이어스 전류값을 이용하여 상기 부하 트랜지스터의 게이트 제어를 통하여 상기 부하 트랜지스터의 드레인-소스 전류를 정전류값으로 상기 복수의 발광다이오드에 입력하여 구동시키는 정전류원 회로;A load transistor for driving the plurality of light emitting diodes and a constant current for inputting and driving the drain-source current of the load transistor to the plurality of light emitting diodes as a constant current value through gate control of the load transistor using a specific bias current value Circle circuit;
    상기 부하 트랜지스터의 드레인-소스 전압과 기준 전압의 차에 비례하는 전압을 상기 전원 공급 회로의 펄스폭 변조 회로로 출력하는 오차증폭기;를 포함하며,And an error amplifier configured to output a voltage proportional to a difference between a drain-source voltage and a reference voltage of the load transistor, to a pulse width modulation circuit of the power supply circuit.
    상기 전원 공급 회로는 상기 오차증폭기에서 입력되는 전압에 따라 상기 출력전압을 가변시키는 것을 특징으로 하는 발광다이오드 구동 회로.The power supply circuit may vary the output voltage according to the voltage input from the error amplifier.
  2. 제1항에 있어서, 상기 오차증폭기는,The method of claim 1, wherein the error amplifier,
    상기 부하 트랜지스터의 드레인-소스 전압을 상기 전원 공급 회로로 피드백시켜 상기 부하 트랜지스터가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 상기 부하 트랜지스터에 인가되도록 상기 전원 공급 회로의 출력전압을 제어하는 것을 특징으로 하는 발광다이오드 구동 회로.Controlling the output voltage of the power supply circuit so that the drain-source voltage of the load transistor is fed back to the power supply circuit so that the minimum drain-source voltage at which the load transistor can operate in a saturation region is applied to the load transistor. A light emitting diode driving circuit.
  3. 제2항에 있어서, 상기 정전류원 회로는,The method of claim 2, wherein the constant current source circuit,
    상기 특정 바이어스 전류값 제어를 통하여 상기 발광다이오드의 광출력을 제어하는 것을 특징으로 하는 발광다이오드 구동 회로.The light emitting diode driving circuit of claim 1, wherein the light output of the light emitting diode is controlled by controlling the specific bias current value.
  4. 제3항에 있어서, 상기 정전류원 회로는,The method of claim 3, wherein the constant current source circuit,
    전류거울(current mirror) 회로와 같은 전류 기준회로(current reference) 또는 달링톤(Darlington) 회로 중에 하나인 것을 특징으로 하는 발광다이오드 구동 회로.A light emitting diode driving circuit, characterized in that it is one of a current reference circuit or a Darlington circuit, such as a current mirror circuit.
  5. 제4항에 있어서, 상기 전원 공급 회로는,The method of claim 4, wherein the power supply circuit,
    Boost 타입, Buck 타입, Buck-Boost 타입 또는 AC-DC SMPS 회로 중에 하나를 포함하는 것을 특징으로 하는 발광다이오드 구동 회로.A light emitting diode driving circuit comprising one of a Boost type, a Buck type, a Buck-Boost type, or an AC-DC SMPS circuit.
  6. 제5항에 있어서,The method of claim 5,
    상기 Boost 타입, Buck 타입 및 Buck-Boost 타입 회로는 펄스폭 변조 방식의 DC-DC 변압 회로인 것을 특징으로 하는 발광다이오드 구동 회로.The Boost type, Buck type and Buck-Boost type circuits are pulse width modulation DC-DC transformer circuits.
  7. 제1항에 있어서,The method of claim 1,
    상기 정전류원 회로는 복수의 부하 트랜지스터를 포함하며, 상기 복수의 부하 트랜지스터에 각각 연결된 복수의 발광다이오드는 병렬로 연결된 것을 특징으로 하는 발광다이오드 구동 회로.The constant current source circuit includes a plurality of load transistors, and the plurality of light emitting diodes respectively connected to the plurality of load transistors are light emitting diode driving circuits, characterized in that connected in parallel.
  8. 제1항 내지 제7항 중 어느 한 항에 있어서, 상기 부하 트랜지스터는,The load transistor according to any one of claims 1 to 7,
    전계 효과 트랜지스터 또는 바이폴라 트랜지스터 중에 하나인 것을 특징으로 하는 발광다이오드 구동 회로.A light emitting diode driving circuit comprising one of a field effect transistor or a bipolar transistor.
  9. 전원 공급 회로는 복수의 발광다이오드에 출력전압을 공급하는 공급 단계;The power supply circuit includes a supply step of supplying an output voltage to the plurality of light emitting diodes;
    정전류원 회로는 특정 바이어스 전류값을 이용하여 부하 트랜지스터의 게이트 제어를 통하여 상기 부하 트랜지스터의 드레인-소스 전류를 정전류값으로 상기 복수의 발광다이오드에 입력하여 구동시키는 구동 단계;The constant current source circuit includes a driving step of inputting and driving the drain-source current of the load transistor to the plurality of light emitting diodes as a constant current value through gate control of the load transistor using a specific bias current value;
    오차증폭기는 상기 부하 트랜지스터의 드레인-소스 전압과 기준 전압의 차에 비례하는 전압을 상기 전원 공급 회로의 펄스폭 변조기로 출력하는 출력 단계;An error amplifier outputting a voltage proportional to a difference between a drain-source voltage and a reference voltage of the load transistor to a pulse width modulator of the power supply circuit;
    상기 전원 공급 회로는 상기 오차증폭기에서 입력되는 전압을 펄스폭 변조 신호로 변환하고 이를 통한 전원 공급회로의 출력전압을 제어하는 제어 단계;를 포함하는 것을 특징으로 하는 발광다이오드 구동 방법.And a control step of converting the voltage input from the error amplifier into a pulse width modulated signal and controlling the output voltage of the power supply circuit.
  10. 제9항에 있어서, 상기 제어 단계는,The method of claim 9, wherein the controlling step,
    상기 오차증폭기는 상기 부하 트랜지스터의 드레인-소스 전압을 상기 전원 공급 회로로 피드백시켜 상기 부하 트랜지스터가 포화영역에서 동작할 수 있는 최소 드레인-소스 전압이 상기 부하 트랜지스터에 인가되도록 상기 전원 공급 회로의 출력전압을 제어하는 것을 특징으로 하는 발광다이오드 구동 방법.The error amplifier feeds back the drain-source voltage of the load transistor to the power supply circuit so that the minimum drain-source voltage at which the load transistor can operate in a saturation region is applied to the load transistor. The method of driving a light emitting diode, characterized in that for controlling.
  11. 제10항에 있어서, 상기 구동 단계에서,The method of claim 10, wherein in the driving step,
    상기 정전류원 회로는 상기 특정 바이어스 전류값 제어를 통하여 상기 발광다이오드의 광출력을 제어하는 것을 특징으로 하는 발광다이오드 구동 방법.And the constant current source circuit controls the light output of the light emitting diode through the control of the specific bias current value.
  12. 제11항에 있어서,The method of claim 11,
    상기 정전류원 회로는 전류거울(current mirror) 회로와 같은 전류 기준회로(current reference) 또는 달링톤(Darlington) 회로 중에 하나인 것을 특징으로 하는 발광다이오드 구동 방법.Wherein said constant current source circuit is one of a current reference circuit such as a current mirror circuit or a Darlington circuit.
  13. 제9항에 있어서,The method of claim 9,
    상기 정전류원 회로는 복수의 부하 트랜지스터를 포함하며, 상기 복수의 부하 트랜지스터에 각각 연결된 복수의 발광다이오드는 병렬로 연결된 것을 특징으로 하는 발광다이오드 구동 방법.The constant current source circuit includes a plurality of load transistors, and a plurality of light emitting diodes connected to the plurality of load transistors, respectively, characterized in that the LED driving method.
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WO2014187004A1 (en) * 2013-05-20 2014-11-27 深圳市华星光电技术有限公司 Led backlight driving circuit, backlight module, and liquid crystal display apparatus
US9237609B2 (en) 2013-05-20 2016-01-12 Shenzhen China Star Optoelectronics Technology Co., Ltd LED backlight driving circuit, backlight module, and LCD device
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CN110838789A (en) * 2018-08-17 2020-02-25 美芯晟科技（北京）有限公司 Ripple suppression circuit, system and method
CN110838789B (en) * 2018-08-17 2021-06-04 美芯晟科技（北京）有限公司 Ripple suppression circuit, system and method
US11075502B2 (en) 2019-08-29 2021-07-27 Analog Devices, Inc. Laser diode driver circuit techniques
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