KR102261852B1 - Ac direct led driver including capacitor for led driver - Google Patents

Abstract

An AC direct type light emitting diode driving device is provided. The AC direct-coupled light emitting diode driving device includes: a rectifying unit; a light emitting diode unit receiving the rectified voltage from the rectifying unit and emitting light; a capacitor for driving the light emitting diode unit during the discharging period while repeating a charging period, a sustain period, a discharge period, and a sustain period according to a preset period; a sequential current driver including a switching element for controlling a path of a current flowing through the light emitting diode unit and the capacitor according to different input voltage levels; a first diode connected between the light emitting diode unit and the first end of the capacitor to form a current path from the light emitting diode unit to the capacitor; and the capacitor connected between the light emitting diode unit and the first end of the capacitor A second diode forming a current path from the light emitting diode unit, and a third diode connected between a ground terminal and a second end of the capacitor to form a current path from the switching element to the capacitor; can do.

Description

AC DIRECT LED DRIVER INCLUDING CAPACITOR FOR LED DRIVER

The present invention relates to an AC direct-coupled light-emitting diode driving device, and more particularly, to an AC direct-connected light-emitting diode driving device including an LED driving capacitor.

In the case of an LED driving device using a converter, the system configuration is complicated and it is difficult to reduce the size and weight of the system. In addition, in order to improve the power factor, a separate power factor correction circuit must be used, and an additional circuit for suppressing the generation of electromagnetic waves generated during switching is required, so that the production cost is high.

On the other hand, in the case of an AC power supply (hereinafter referred to as AC) direct-connected linear type LED driving device that does not use a separate converter, the current is directly controlled using AC power, which is a commercial power source, so the circuit is simpler and power factor compared to the converter type. However, it exhibits excellent characteristics even without an additional correction circuit in preparation for electromagnetic wave generation. In addition, there is an advantage of a long lifespan and high reliability compared to a converter method, that is, a switching mode power supply (SMPS). In addition, the AC power direct-connected linear driving method has a good power factor characteristic because current switching occurs in such a way that the driving current increases as the input voltage increases.

However, in the AC direct-connected linear driving method, especially in the sequential driving method, the light emitting diodes of each channel are sequentially driven according to the magnitude of the input voltage, that is, the channels are driven with unequal driving times and unequal driving current sizes. The current deviation between channels is large.

In order to improve the current deviation, a synchronous multi-channel driving method has been proposed to minimize the temporal driving current deviation, but there is still a deviation in the magnitude of the driving current proportional to the input voltage.

In addition, in the case of the AC direct drive method, when the input voltage is lower than the minimum light emitting diode voltage drop, current is not supplied, so there is a problem in that flicker occurs. Therefore, in order to improve the flicker characteristics, a capacitor serving as an energy storage for driving the light emitting diode during a time when power is not supplied should be used. A method of supplying current to the light emitting diode with the voltage stored in the capacitor while the input voltage is lower than the light emitting diode voltage by using a capacitor at the input terminal or by using a capacitor in parallel with the light emitting diode is widely used.

1 is a diagram illustrating a conventional linear light emitting diode driving circuit using a filter capacitor at an input stage, and shows a light emitting diode driving circuit in which flicker is reduced by using a capacitor at the input stage. FIG. 2 is a graph showing voltage and current waveforms in the circuit of FIG. 1 .

As shown, the rectifier _{receives the AC power voltage from the AC power supply (VAC} ), rectifies the applied voltage, and serves to supply it to the light emitting diode unit (LED). This rectified voltage is charged in the capacitor and used as the driving voltage of the LED.

2 shows the rectified input power (V _IN ), the current (I _LED ) and the input current (I _IN ) flowing through one light emitting diode.

When the input power V _IN is charged in the capacitor, a charging voltage lower than the input power becomes a reference voltage, and the flow _{of the input current I IN is controlled according to the reference voltage.} As shown, in the conventional case, a high charging current (I _IN ) occurs during a short charging time.

In the case of the driving device as shown in FIG. 1, when the LED voltage is set lower than the rectified input voltage and driven, the percentage flicker can be satisfied even to “0%”, but the inrush current is a big problem because the capacitor needs to be charged with a high current for a short time. there is In addition, since the power factor is very low (0.6 or less) and THD shows a high value of 40% or more, it is very limited in terms of application.

In summary, the method as shown in FIG. 1 in which a light emitting diode is driven with a rectified voltage using a capacitor at the input terminal through a rectifier has very improved flicker characteristics, but a large current is generated when power is applied, which can be converted into an inrush current during parallel operation of multiple lights. Due to this, there is a risk that the overcurrent circuit breaker will operate, and there is a problem that a large inrush current is continuously generated when the triac is used. In addition, its use is limited due to poor power factor and THD characteristics.

3 is a diagram showing a two-channel sequential light emitting diode driving circuit using a capacitor in parallel to a conventional light emitting diode, and FIG. 4 is an input voltage, input current, capacitor voltage and current flowing through the light emitting diode in the circuit of FIG. It is a graph.

As shown, the driving circuit includes capacitors C1 and C2 connected in parallel to two channels of LED 1 and LED 2, and a switch unit for controlling on/off of LED 1 and LED 2 .

As shown in FIG. 4 , when the operating AC voltage increases and _{becomes greater than the threshold voltage (V LED1} ) of the first LED 1 of the light emitting unit, a sequential current driving unit composed of two N-type MOSFETs connected in a source-couple-pair form and a resistor By operation, the first switch element is in an On state. Accordingly, a current path is formed through the first LED 1 and the first switch element, and the first LED 1 emits light. At this time, a current (I _{1 ) as shown in the first graph flows through the switch driving LED 1, and a current (I LED1} ) as shown in the fourth graph flows through LED 1 to which the capacitor C1 is connected.

After that, when the operating AC voltage increases and _{becomes greater than the threshold voltage (V LED2} ) of the second LED 2 , the first switch element is in an off state, and the second switch element is in an on state. As a result, a current path is formed through the two LEDs 1 and 2 and the second switch element, and LED 1 and LED 2 emit light.

Then, when the operating AC voltage decreases, the switch elements are sequentially turned off, so that LED 1 and LED 2 do not sequentially emit light.

Similarly, a current (I _{2 ) as shown in the second graph flows through the switch driving LED 2, and a current (I LED2} ) as shown in the fifth graph flows through LED 2 to which the capacitor (C2) is connected.

As shown, inrush current, which is a problem of the driving device of FIG. 1 , does not occur, and characteristics such as power factor and efficiency such as THD are greatly improved compared to FIG. 1 by two-channel operation. On the other hand, the method of using a capacitor in parallel with the light emitting diode is similar to the method not using a capacitor in terms of power factor and THD characteristics. There is a disadvantage in that a capacitor having a capacitance must be used. In the case of the driving circuit according to FIG. 3 , there is a disadvantage in that a capacitor having a very large capacitance compared to FIG. 1 must be used in order to satisfy the percentage flicker characteristic at a value of 20% or less.

The conventional AC direct drive method requires a light emitting diode voltage proportional to the input voltage to increase efficiency, so when a single light emitting diode having the same voltage drop is used, a converter method that uses a low light emitting diode voltage A much larger number of light emitting diodes must be used compared to that.

In addition, when using the AC direct drive method, even in the case of a small light consuming low power, the voltage drop of the light emitting diode must satisfy the condition that the voltage drop of the light emitting diode should be about 70 ~ 90% of the input voltage. A light emitting diode with a high diode voltage drop must be used.

As described above, the number of LEDs used in the AC direct drive method is greater than that of lighting using a converter, so a new type of AC direct drive method operating at a low LED voltage drop is required in order to reduce the manufacturing cost.

In addition, there is an active movement to further strengthen the flicker regulation for LED lighting in recent years. The rationale for the tightening is because research reports that prolonged exposure to high-percentage flicker lighting can cause problems such as dizziness and seizures in sensitive people. An LED driving method that satisfies the new flicker characteristics that is expected to be strengthened in the future, has high efficiency, and does not use an inductor or transformer, is required.

Patent Publication 10-2016-0137012 Registered Patent 10-1198408

An object of the present invention is to provide an AC direct-connected light emitting diode driving device including an LED driving capacitor having improved flicker characteristics.

In addition, the problem to be solved by the present invention is to provide an AC direct-connected light emitting diode driving device including an LED driving capacitor that satisfies high efficiency, high power factor and low THD characteristics.

An object of the present invention is to provide an AC direct-connected light emitting diode driving device using a small number of light emitting diodes and including an LED driving capacitor.

A light emitting diode driving apparatus according to an embodiment of the present invention includes: a rectifying unit for receiving and rectifying an AC power voltage; a light emitting diode unit receiving the rectified voltage from the rectifying unit and emitting light; a capacitor for driving the light emitting diode unit during the discharging period while repeating a charging period, a sustain period, a discharge period, and a sustain period according to a preset period; A sequential current driver comprising: a switching element for controlling a path of a current flowing through the light emitting diode unit and the capacitor according to different input voltage levels; and a resistor connected to the switching element and a ground terminal to control a driving current of the switching element. Wow; a first diode connected between the light emitting diode unit and the first end of the capacitor to form a current path from the light emitting diode unit to the capacitor; and a first diode connected between the light emitting diode unit and the first end of the capacitor and the capacitor A second diode forming a current path from the light emitting diode unit, and a third diode connected between a ground terminal and a second end of the capacitor to form a current path from the switching element to the capacitor; can do.

According to an embodiment of the present invention, there is provided an AC direct-connected light emitting diode driving device including an LED driving capacitor having improved flicker characteristics.

According to an embodiment of the present invention, there is provided an AC direct-connected light emitting diode driving device including an LED driving capacitor satisfying high efficiency, high power factor, and low THD characteristics.

According to an embodiment of the present invention, there is provided an AC direct-connected light emitting diode driving device using a small number of light emitting diodes and including an LED driving capacitor.

Through this, since a high-frequency switching operation is not involved, there is no need for a noise filter such as an EMI filter, so that the entire system is very simple and an AC direct-connected light emitting diode driving device capable of reducing manufacturing cost can be provided.

1 is a diagram illustrating a conventional linear light emitting diode driving circuit using a filter capacitor at an input terminal.
FIG. 2 is a graph showing voltage and current waveforms in the circuit of FIG. 1 .
3 is a diagram illustrating a two-channel sequential light emitting diode driving circuit using a capacitor in parallel to a conventional light emitting diode.
4 is a graph illustrating an input voltage, an input current, a capacitor voltage, and a current flowing through a light emitting diode in the circuit of FIG. 3 .
5 is a circuit diagram of an AC direct-coupled light emitting diode driving device including an LED driving capacitor according to an embodiment of the present invention.
6 is a graph illustrating currents flowing through important devices and voltages of important nodes, such as input voltage, input current, capacitor voltage, and current flowing through a light emitting diode, when the circuit of FIG. 5 operates in a normal state.
7A to 7D are diagrams illustrating driving current paths for each of 4 sections of the capacitor in FIG. 5 .
8 is a circuit diagram of an AC direct-coupled light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. It is a circuit diagram for allowing a constant current to flow through the light emitting diode by adding a current mirror between the sequential driving current unit and the light emitting diode to correct the driving current difference caused by the switching operation of the sequential driving current unit.
9 is a graph illustrating currents flowing through important elements and voltages of important nodes, such as input voltage, input current, capacitor voltage, and current flowing through a light emitting diode, when the circuit of FIG. 8 operates in a normal state.
FIG. 10 is a diagram illustrating a general 4-channel AC light emitting diode driving circuit having the same function of making the current of the light emitting diode using the current mirror of FIG. 8 as the same. The current of the light emitting diode flows sequentially according to the magnitude of the input voltage, but the driving current becomes the same.
11 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. By using a capacitor in parallel with the light emitting diode, it serves to reduce the current reduction that occurs when switching from M1 to M2 or M2 to M1 during sequential current driver operation.
12 is a view in which an operational amplifier is added to a sequential current driving unit in the driving device of FIG. 5 according to an embodiment of the present invention.
FIG. 13 is a view showing a function of making the current of the light emitting diode using a current mirror the same in the driving device of FIG. 12 according to an embodiment of the present invention is applied.
14 is a diagram in which a sequential current driver is implemented as a cascode circuit in the driving device of FIG. 5 according to an embodiment of the present invention.
FIG. 15 is a view showing a function of making the current of a light emitting diode using a current mirror the same in the driving device of FIG. 14 according to an embodiment of the present invention is applied.
FIG. 16 is a view in which an op amp is added to a sequential current driving unit in the driving device of FIG. 14 according to an embodiment of the present invention.
FIG. 17 is a view showing the application of a function of making the current of the light emitting diode using a current mirror the same in the driving device of FIG. 16 according to an embodiment of the present invention.
18 is a diagram illustrating a circuit in which the position of D4 is changed between the sources of Rs and M2 of the sequential current driving unit in the driving device of FIG. 5 according to an embodiment of the present invention.
19 is a view showing a function for making the current of the light emitting diode equal to the current using the current mirror is applied in the driving device of FIG. 18 according to another embodiment of the present invention.
20 is a view in which an operational amplifier is added to a sequential current driving unit in the driving device of FIG. 18 according to another embodiment of the present invention.
FIG. 21 is a view showing a function of making the current of a light emitting diode equal to that of a light emitting diode using a current mirror is applied in the driving device of FIG. 20 according to another embodiment of the present invention.
22 is a diagram in which a sequential current driver is implemented as a cascode circuit in the driving device of FIG. 18 according to an embodiment of the present invention.
FIG. 23 is a view showing a function for making the current of a light emitting diode equal to that of a light emitting diode using a current mirror is applied in the driving device of FIG. 22 according to another embodiment of the present invention.
24 is a diagram illustrating a circuit in which the position of D4 is changed between the source of M2 of the sequential current driver and the source of M4 of the cascode circuit in the driving device of FIG. 22 according to an embodiment of the present invention.
FIG. 25 is a view showing a function for making the current of a light emitting diode equal to that of a light emitting diode using a current mirror is applied in the driving device of FIG. 24 according to another embodiment of the present invention.
26 is a view in which an operational amplifier is added to a sequential current driving unit in the driving device of FIG. 22 according to another embodiment of the present invention.
FIG. 27 is a view showing a function of making the current of a light emitting diode equal using a current mirror is applied in the driving device of FIG. 26 according to another embodiment of the present invention.
28 is a view in which an operational amplifier is added to a sequential current driving unit in the driving device of FIG. 24 according to another embodiment of the present invention.
FIG. 29 is a view showing a function of making the current of the light emitting diodes using a current mirror the same in the driving device of FIG. 28 according to another embodiment of the present invention is applied.
30A to 30E are diagrams showing a circuit that can be used as a current mirror according to an embodiment of the present invention. Although only the drawings using PMOS are shown, the same configuration is possible with PNP transistors.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited only to the embodiments described below. The shapes and sizes of elements in the drawings may be exaggerated for clearer description, and elements indicated by the same reference numerals in the drawings are the same elements.

On the other hand, the meaning of the terms described in the present application should be understood as follows.

Terms such as “first” and “second” are for distinguishing one component from another, and the scope of rights should not be limited by these terms. For example, a first component may be termed a second component, and similarly, a second component may also be termed a first component.

And throughout the specification, when a part is "connected" with another part, it includes not only the case where it is "directly connected" but also the case where it is "electrically connected" with another element interposed therebetween. In addition, when a part "includes" or "includes" a certain component, it means that other components may be further included or provided without excluding other components unless otherwise stated. .

5 is a circuit diagram of an AC direct-coupled light emitting diode driving device including an LED driving capacitor according to an embodiment of the present invention.

As shown, the light emitting diode driving device according to the present embodiment includes a rectifier 100, a light emitting diode unit (LED, 200), a capacitor (C, 300), a sequential current driving unit 400 and a charge/discharge control unit 500. may include

The rectifying unit 100 receives an AC power voltage from the AC power source (AC), rectifies the applied voltage, and supplies the rectified current to the light emitting diode unit 200 . As shown, the rectifying unit 100 may be a bridge diode, but is not limited thereto, and any circuit can be used as long as it can convert an alternating current that changes in both positive and negative directions into a current having only one direction. can be implemented.

The light emitting diode unit 200 receives the rectified voltage from the rectifier 100 to emit light, and may be implemented as a channel to which at least one light emitting diode connected to each other is connected. The number and connection method (series or parallel) of the light emitting diodes included in the light emitting diode unit 200 can be variously modified depending on the type of lighting to be used for the driving device, and the light emitting diodes constituting one channel are simultaneously turned on or turns off

The capacitor 300 is connected to a current path flowing through the light emitting diode unit 200 and repeats a charging section, a sustain section, a discharging section, and a sustain section according to a preset cycle. In addition, the capacitor 300 drives the light emitting diode unit 200 with the voltage charged during the discharging period, and charging and discharging of the capacitor 300 is controlled by a plurality of diodes included in the charging/discharging control unit 500 . do.

The sequential current driving unit 400 is a switching device (S1, S2) that controls a path of current flowing through the light emitting diode unit 200 and the capacitor 300 according to different input voltage levels, and is a MOSFET (Metal-Oxide-Semiconductor Field). It may include -Effect Transistor), and is connected to the switching element (S1, S2) and the ground terminal comprises a resistor (R _S) for controlling the driving current of the switching element (S1, S2).

The switching elements S1 and S2 according to the present embodiment include a first switching element S1 and a second switching element S2, and the first end of the first switching element S1 is a light emitting diode unit 200 . and connected between the first diode 510 of the charge-discharge control unit 500 to be described below, the second stage is connected to the resistance (R _S), it is supplied with a driving power source through the third stage.

Similarly, the second first stage of the switching device (S2) is connected to the second terminal of the capacitor 300, the second end is connected to a resistor (R _S), it is supplied with a driving power source through the third stage .

The first switching element S1 and the second switching element S2 may be formed of a Bipolar Junction Transistor (BJT) or an Insulated Gate Bipolar Transistor (IGBT) in addition to a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).

The sequential current driving unit 400 supplies current to the light emitting diode unit 200 through the first switching element S1 when the input voltage or the voltage of the capacitor 300 is higher than the driving voltage of the light emitting diode unit 200 and input When the voltage is higher than the sum of the driving voltage of the light emitting diode unit 200 and the voltage of the capacitor 300, the second switching element S2 serves to supply current to the light emitting diode unit 200 and the capacitor 300 do.

The charge/discharge control unit 500 controls the charging and discharging of the capacitor 300 according to a predetermined cycle, and a first diode 510 , a second diode 520 , and a third diode 530 for controlling a current path. include

The first diode 510 is connected between the light emitting diode unit 200 and the first end of the capacitor 300 to form a current path from the light emitting diode unit 200 to the capacitor 300 , and the second diode 520 . is connected between the light emitting diode unit 200 and the first end of the capacitor 300 to form a current path from the capacitor 300 to the light emitting diode unit 200 . The third diode 530 is connected between the ground terminal and the second terminal of the capacitor 300 to form a current path from the switching elements S1 and S2 to the capacitor 300 .

When the input voltage is greater than the sum of the driving voltage of the light emitting diode unit 200 and the voltage of the capacitor 300 , the charge/discharge control unit 500 sequentially controls the current flowing through the second switching element S2 determined by the current driving unit 400 ( I _M2 ) provides a path for driving the light emitting diode unit 200 and charging the capacitor 300 .

If the input voltage is smaller than the charging voltage stored in the capacitor 300 , the charging/discharging control unit 500 uses a current flowing through the first switching element S1 determined by the sequential current driving unit 400 , and the capacitor 300 is the light emitting diode unit. If a discharge path for driving 200 is provided, and the input voltage is greater than the charging voltage stored in the capacitor 300 , but smaller than the sum of the charging voltage of the capacitor 300 and the driving voltage of the light emitting diode unit 200 , Control to maintain the charging voltage of the capacitor 300 by blocking the charging/discharging path. During the period in which the charging/discharging path of the capacitor 300 is blocked, the light emitting diode unit 200 is driven by the _{current I M1 flowing through the first switching element S1 determined by the sequential current driving unit 400 through the input voltage.}

With this operation, there is no section in which the current flowing through the light emitting diode unit 200 decreases to “0A” in the steady-state condition), and the current flowing through the light emitting diode unit 200 is the I _M1 minimum current. The maximum current will be I _M2 .

As shown, the first switching element and the second switching element constituting the sequential current driving unit 400 of the AC direct-coupled light emitting diode driving device according to the present embodiment are a first MOSFET 410 and a second MOSFET 420 . , and the charge/discharge control unit 500 further includes a fourth diode 540 in addition to the first diodes 510 to 530 .

The drain terminal of the first MOSFET (410) is connected between the LED 200 and the first diode 510, a source terminal is connected to one end of the resistor (R _S). The drain terminal of the MOSFET 2 (420) is connected on the path to the capacitor 300, the source terminal is connected to one end of the resistor (R _S).

The fourth diode 540 is connected on a path through which the capacitor 300 and the second MOSFET 420 are connected, that is, a current path between the capacitor 300 and the second MOSFET 420 . The fourth diode 540 corresponds to a necessary component when the switching element of the sequential current driver 400 is implemented as a MOSFET. If the switching element is implemented as a BJT or an IGBT, the fourth diode 540 may be omitted because there is no diode characteristic present in the switching element.

The fourth diode 540 serves to prevent current from flowing from the first MOSFET 410 to the second MOSFET 420 during the discharge period of the capacitor 300 . In other words, due to the source-drain voltage of the second MOSFET 420 while the capacitor 300 is discharging, the path of the discharge current _{does not pass through the resistor R S and} passes from the source terminal of the first MOSFET 410 to the second It functions to prevent flow in the source-drain direction of the MOSFET 420 .

If the fourth diode 540 is not used, the current flowing through the light emitting diode unit 200 during the discharge period is not determined to the value set in the first MOSFET 410 , and the voltage stored in the capacitor 300 is Flicker characteristics may be deteriorated by flowing into the light emitting diode unit 200 at a large current value and immediately discharging it. Hereinafter, the current flow in the charging and discharging sections will be described with reference to FIGS. 7A to 7D .

Meanwhile, as described above, the fourth diode 540 may be disposed on the current path of the capacitor 300 and the second MOSFET 420. According to this embodiment, the fourth diode 540 is a capacitor ( It is disposed between 300 and the second MOSFET 420 . Specifically, the anode of the fourth diode 540 is connected to the second terminal of the capacitor 300 , and the cathode is connected to the drain terminal of the second MOSFET 420 .

6 is a graph showing the current flowing through important elements and voltages of important nodes, such as input voltage, input current, capacitor voltage, and current flowing through the light emitting diode, when the circuit of FIG. 5 operates in a normal state, and FIGS. 7A to 7D FIG. 5 is a diagram showing the driving current path for each of the 4 sections of the capacitor.

As described above, the first MOSFET 410 is turned on when the input voltage (V _{IN ) is less than the charging voltage (V C} ) stored in the capacitor 300 , and the current flowing through the first MOSFET 410 (I _M1 ) The capacitor 300 provides a discharge path for driving the light emitting diode unit 200 . Further, the input voltage (V _IN) driving voltage (V _LED) of the charging voltage (V _C) and the LED unit 200 of the charging voltage (V _C), the capacitor 300 is larger than than that stored in the capacitor 300, The first MOSFET 410 is turned on even when it is smaller than the sum of .

The second MOSFET 420 is turned on when the input voltage V _{IN is greater than the sum of the driving voltage V LED} of the light emitting diode unit 200 and the voltage V _C of the capacitor 300 , and the second MOSFET ( The light emitting diode unit 200 is driven by _{the current I M2} flowing through the 420 , and the capacitor 300 is charged.

_{The current I M1} flowing through the first MOSFET 410 _{and the current I M2} flowing through the second MOSFET 420 may be expressed by Equation 1 below.

[Equation 1]

I _M1 = (V ₁ - V _GS,M1 ) / R _S

I _M2 = (V ₂ - V _GS,M2 ) / R _S

On the other hand, it can be described by separating the operation state according to the voltage (V _C) of the voltage (V _LED) and the capacitor 300 of the input voltage (V _IN) size and a light emitting diode unit 200 of the four sections of the The conditions for dividing each section are as follows.

[Equation 2]

Section 1: V _C - V _D2 - V _D3 < V _IN < V _C + V _LED + V _D1 + V _D4 (maintain C voltage)

Section 2: V _IN > V _C + V _LED + V _D1 + V _D4 (C charging section)

Section 3: V _C - V _D2 - V _D3 < V _IN < V _C + V _LED + V _D1 + V _D4 (maintain C voltage)

Section 4: V _IN < V _C - V _D2 - V _D3 (C discharge section)

A path through which a driving current flows through the light emitting diode unit 200 and the capacitor 300 in each section is shown in FIG. 7 . For the sake of simplicity of description, the voltage drop of the diodes 510 to 540 having a relatively small voltage drop is not considered in the above equation.

In section 1 (P 1), the input voltage (V _IN ) is higher than the voltage (V _{C, MIN} ) stored in the capacitor 300 , and the maximum charging voltage (V _{C, MAX} ) of the capacitor 300 and the light emitting diode unit 200 . It corresponds to a section lower than the sum of the driving voltages (V _LED ) (V _LED + V _{C, MAX ).} At this time, the first MOSFET 410 is turned on, and the current I _M1 flowing through the first MOSFET 410 drives the light emitting diode unit 200 ( FIGS. 6A and 6D ). In this case, the second MOSFET 420 is turned off (FIG. 6 (b)), and the capacitor 300 maintains a constant charging voltage without charging or discharging (FIG. 6 (e), (f)) .

FIG. 7A shows the current flow in this holding period, and the driving current I _LED of the light emitting diode unit 200 is equal to the input current I _IN ( FIG. 6C ).

Region 2 (P 2) is the sum of a charging interval of the capacitor 300, the input voltage (V _IN) driving voltage (V _LED) of the voltage (V _C) and the LED 200 of the capacitor 300 ( V _LED +V _{C, MAX} ) as the drain voltage of the second MOSFET 420 rises, the first MOSFET 410 is turned off (FIG. 6 (a)), and the second MOSFET 420 is turned on _{This is a section through which the current I M2} set in the second MOSFET 420 flows (FIG. 6(b)).

The generated current I _M2 flows as shown in FIG. 7B , and drives the light emitting diode unit 200 and simultaneously charges the capacitor 300 , and the charging voltage V _C of the capacitor 300 increases ( FIG. 6 ). of (e), (f)). In this section, the input current I _{IN becomes equal to the current I M2} flowing through the second MOSFET 420 (FIG. 6 (b), (c)). When this is observed together with the case of section 1 of FIG. 7A , the input current (I _IN ) is in the form of a two-step step increasing _{from I M1} to the set current (I _{M2 ) of the second MOSFET 420 , which is one channel} Although using the light emitting diode unit 200 of the input current (I _IN ) is formed similarly to the two-channel driving method. Through such current control, power factor and efficiency are increased compared to 1-channel driving.

In section 3 (P 3), the input voltage (V _IN ) is lowered and the input voltage (V _IN ) is higher than the capacitor 300 voltage (V _C ), but the voltage of the capacitor 300 and the driving of the light emitting diode unit 200 . In a period smaller than the sum (V _LED +V _{C, MAX ) of the voltage (V LED} ), the second MOSFET 420 is turned off again and the first MOSFET 410 is turned on. _{In this section, the light emitting diode unit 200 is driven by the current I M1} flowing through the first MOSFET 410 as in the path of FIG. 7c ((a), (c) of FIG. 6), and the capacitor 300 is _{The charging voltage V C} is maintained due to the turn-off of the second MOSFET 420 ( FIG. 6 (e), (f)).

Section 4 (P 4) is a section in which the input voltage (V _IN ) continuously decreases after section 3 and becomes _{smaller than the voltage (V C, MAX} ) of the capacitor 300, the first MOSFET 410 is turned on, and the second 2 MOSFET 420 is turned off. As the capacitor 300 is discharged, a _{current path as shown in FIG. 7D in which the voltage V C} of the capacitor 300 drives the light emitting diode unit 200 is formed, and at this time, the driving current of the light emitting diode unit 200 ( I _{LED ) becomes a current I M1} flowing through the first MOSFET 410 . That is, in section 4, there is no input current by _VAC and the capacitor 300 is discharged while driving the light emitting diode unit 200 with _{I M1 .}

At this time, the discharged capacitor 300 voltage (V _C ) is maintained in the subsequent section 1, and repeats the charging operation in the second section. As such, during the repetition of the four sections, the minimum value _{of the current (I LED ) of the light emitting diode unit 200 becomes I M1} and the maximum value becomes I _M2 , so that the flicker characteristics are improved as well as the power factor and efficiency compared to one channel. perform an ascending motion. The percentage flicker characteristic can be expressed by the following equation.

[Equation 3]

Percentage Flicker (%) = [(I _M2 - I _M1 )*100]/(I _M1 + I _M2 )

In addition, since the voltage of the second stage of the capacitor 300 does not stop flowing in the light emitting diode unit 200 and is maintained at a certain level or more, it has a shape as shown in (g) of FIG. 6 .

In this operation, the maximum charging voltage (V _C,MAX ) of the capacitor 300 is obtained by subtracting _{the voltage drop (V LED} ) of the light emitting diode unit 200 from the maximum instantaneous voltage (V _IN,PEAK ) of the input voltage (V _{IN )} value and the minimum voltage (V _C,MIN ) of the capacitor 300 is the voltage (V _LED ) of the light emitting diode unit 200 . Schematic of this relationship is shown in Equation 4 below. In Equation 4, voltage drop by the first diode 510 to the fourth diode 540 is ignored for the sake of simplification of operation description.

[Equation 4]

V _{C, MAX} = V _{IN, PEAK} - V _LED

V _C,MIN = V _LED

As described above, in order to improve the flicker characteristic, the light emitting diode unit 200 should be driven in all sections. During section 4, that is, in order to drive the light emitting diode unit 200 with _{the discharge voltage V C} of the capacitor 300 rather than the input power _{, the charging voltage V C} of the capacitor 300 is the light emitting diode unit 200 . It is preferable that the capacitance of the capacitor 300 be sufficiently large to be maintained greater than the driving voltage V _{LED .}

If the maximum charging voltage (V _{C, MAX ) is greater than the driving voltage (V LED} ) of the light emitting diode unit 200, the driving of section 4 is possible through the capacitor 300 having a small capacitance, but the efficiency may be reduced. .

In addition, as the value of the capacitance increases, the ripple voltage of the charging/discharging capacitor decreases, and the average value of the charging voltage _{V C of the} capacitor 300 increases as it approaches the _{maximum charging voltage V C and MAX .}

On the other hand, as the capacitor voltage (V _C ) approaches the driving voltage (V _LED ) of the light emitting diode unit 200 , the efficiency can be increased, but to 90% of the steady state in which the light emitting diode unit 200 is driven. If it drops, the capacitor voltage V _C may be insufficient, and the flicker characteristic may deteriorate. The voltage charged and discharged in the capacitor 300 may be expressed by Equation 5 below.

[Equation 5]

V _C,CHARGE = I _M2 × t _P2 / C

V _C,DISCHARGE = I _M1 × t _P4 / C

here,

t _P2 : holding time of section 2 (charging time)

t _P4 : holding time of section 4 (discharge time)

V _C,CHARGE : Capacitor voltage when charging

V _C,DISCHARGE : capacitor voltage during discharge

As described above, in the normal state, since the amount of charge and the amount of discharged charge are the same, _{as I M2} is large, the charging time is relatively shorter than the discharging time.

According to the embodiment described with reference to FIGS. 6 and 7 , the light emitting diode driving device includes a capacitor for driving the light emitting diode unit and has low flicker characteristics without a configuration such as a transformer, and has fewer numbers than the existing two-channel driving method. Since it can be used as a channel for the light emitting diode of the LED, it can reduce the manufacturing cost and increase the efficiency and power factor compared to the existing one-channel driving method.

8 is an AC direct-connected light emitting diode driving device according to the present embodiment by adding a current mirror 600 between the light emitting diode unit 200 and the first MOSFET 410 of the sequential current driving unit 400 to the first MOSFET ( 410) At turn-on, the current of the sequential current driving unit 400 is the same, but by increasing the light-emitting diode driving current, the current flowing through the light-emitting diode unit 200 when the first MOSFET 410 and the second MOSFET 420 is turned on is the same. perform the function In the general sequential current driver 400 , the driving current of the second MOSFET 420 is always greater than the driving current of the first MOSFET 410 due to the driving characteristics. However, it is possible to obtain the effect of further improving the flicker characteristics by making the current flowing through the light emitting diode unit 200 the same without changing the values of _{I M1} and I _{M2 .}

In FIG. 8 , if the W/L size ratio of the two PMOSFETs used in the current mirror 600 is k, the light emitting diode driving current when the first MOSFET 410 is turned on is generated by the current flowing _{in I M1 and the current mirror 600 .} It is expressed as the sum of the currents

[Equation 6]

I _LED = I _M1 (1 + k)

_{Since I M2} is always _{larger than I M1} due to the operation characteristics of the sequential current driver _{, I M1} and I _M2 can be set equal by adjusting the k value, which is the size ratio of the two MOSFETs. As a result, the same current always flows through the light emitting diode unit 200, so that the flicker characteristic is greatly improved. FIG. 9 shows voltages and currents of important nodes in FIG. 8 .

The current mirror 600 may be a circuit having a characteristic of generating a current proportional to the current formed by the sequential current driver due to the operational characteristics, for example, a cascode current mirror circuit, a Wilson current mirror circuit, a Weedler current mirror circuit. and a current mirror circuit using an amplifier (hereinafter, FIGS. 30A to 30E).

As such, the method of maintaining the same current of the light emitting diode unit 200 while maintaining the sequential driving characteristics by using the current mirror 600 in the sequential current driving unit 400 is very important considering the recent lighting trend in which the flicker characteristics are important. It is a useful driving technique. However, if the LED driving current is set to be the same, the input current does not rise or fall in 2-steps, but becomes a 1-step pulse wave, and the power factor and THD characteristics are slightly deteriorated. Nevertheless, the percentage flicker can theoretically be made '0%', so it can be usefully used in the case of lighting where the flicker characteristic is very important.

The circuit in which the current mirror 600 having these characteristics is applied to the sequential current driver 400 is applicable not only to the two-channel driving but also to the number of channels higher than that. 10 shows an example of a 4-channel light emitting diode driving circuit in which a current mirror is included in a sequential current driving unit. In the case of 4 channels, three current mirrors are required, and when the k value of each current mirror is determined as follows, the current flowing through each light emitting diode by the sequential current driver becomes the same.

[Equation 7]

I _M4 = (1 + k ₃ ) * I _M3 = (1 + k ₂ ) * I _M2 = (1 + k ₁ ) * I _M1

In the conventional sequential current driver, the magnitude of the current is in the order of I _M4 > I _M3 > I _M2 > I _M1 due to the characteristics of operation, and sequentially increases/decreases in proportion to the magnitude of the input voltage. When a current mirror as shown in FIG. 10 is connected here, the current flowing through each light emitting diode becomes the same according to the set value of k. Since it is not a synchronous driving method, the current flowing through the light emitting diodes is the same, but they are sequentially driven, so that the remaining channels 2, 3, and 4 are turned off during the period in which the first channel is driven. However, when a current mirror is used for two channels including one light emitting diode channel and one capacitor as shown in FIG. 8 of the present invention, the current flowing through the light emitting diode is driven with the same current over the entire period.

11 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. The AC direct-connected light emitting diode driving apparatus according to the present embodiment further includes a parallel capacitor 310 to be connected in parallel to the light emitting diode unit 200 . A decrease in current of the light emitting diode unit 200 caused by current switching between the first MOSFET 410 and the second MOSFET 420 is reduced by the added parallel capacitor 310, and the flicker characteristic is improved. Since the current switching time is short, the current reduction can be reduced even with a small capacitor value.

12 is a circuit diagram of an AC direct-coupled light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, the sequential current driver 400 includes a first operational amplifier 430 having an output terminal connected to the gate terminal of the first MOSFET 410 and an output terminal connected to a gate terminal of the second MOSFET 420 . It further includes a second operational amplifier (440).

_{The time at which the current I M1 flowing through the first MOSFET 410 and the current I M2} flowing through the second MOSFET 420 cross due to the use of the first operational amplifier 430 and the second operational amplifier 440 . In addition to this reduction, the output impedance is increased, and _{the influence of V GS} when setting _{I M1} and I _M2 can be eliminated, thereby minimizing the amount of fluctuation of the driving current caused by the temperature or process parameter change of the driving current.

5 to 12 as well as in all the following embodiments of the present invention, a switching element that does not include an anti-parallel diode between the drain and the source such as IGBT and BJT can be used to replace the first and second MOSFETs of the sequential current driver, In this case, the fourth diode may be omitted.

13 is a circuit diagram of an AC direct-coupled light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 12 according to another embodiment of the present invention, a current mirror 600 is added between the light emitting diode unit 200 and the first MOSFET 410 of the sequential current control unit 400 to add the first When the MOSFET 410 is turned on, the current of the sequential current controller is the same, but increases the driving current of the light emitting diode to make the current flowing through the light emitting diode equal when the first MOSFET 410 and the second MOSFET 420 are turned on. In addition to FIGS. 8 to 13 , in order to improve the flicker characteristics in all embodiments below, the driving current may be equalized by using a current mirror in the sequential current driving unit.

14 is a circuit diagram of an AC direct-coupled light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, the sequential current driver 400 according to the present embodiment additionally includes a third MOSFET 450 and a fourth MOSFET 460 to constitute a cascode type circuit. Specifically, the third MOSFET 450 is connected in series to the drain terminal of the first MOSFET 410 and corresponds to the first cascode element to which the bias voltage is applied to the gate terminal, and the fourth MOSFET 460 is the second MOSFET 460 . 2 Corresponds to the second cascode element connected in series to the drain terminal of the MOSFET 420 and to which the bias voltage is applied to the gate terminal.

The use of the cascode circuit increases the output impedance, thereby minimizing the fluctuation of the driving current due to the fluctuation of the drain voltage.

15 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, light is emitted by adding a current mirror 600 between the first MOSFET 410 and the third MOSFET 450 of the sequential current control unit formed in the cascode in the drawing of FIG. 14 according to another embodiment of the present invention. It performs the function of making the current flowing through the diode equal.

16 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 14 according to another embodiment of the present invention, the output terminal is connected to the gate terminal of the first MOSFET 410 to the sequential current driver 400, the first operational amplifier 430, and 2 This shows a circuit in which driving characteristics are improved by further including a second operational amplifier 440 having an output terminal connected to the gate terminal of the MOSFET 420 .

17 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 16 according to another embodiment of the present invention, a current mirror 600 is added between the first MOSFET 410 and the third MOSFET 450 of the sequential current controller 400 to add a light emitting diode. It performs the function of making the current flowing in the same

18 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the charge/discharge control unit 500 according to the present embodiment, the fourth diode 540 is connected to the source terminal of the second MOSFET 420 rather than the drain terminal of the second MOSFET 420 . That is, the fourth diode 540 has its anode connected to the source terminal of the MOSFET 2 (420), the cathode is connected to a resistor (R _S).

As described above, the fourth diode 540 serves to prevent current from flowing from the first MOSFET 410 to the second MOSFET 420 during the discharge period of the capacitor 300 . In other words, due to the source-drain voltage of the second MOSFET 420 while the capacitor 300 is discharging, the path of the discharge current _{does not pass through the resistor R S and} passes from the source terminal of the first MOSFET 410 to the second It functions to prevent flow in the source-drain direction of the MOSFET 420 . For the movement of the position of the fourth diode 540 , a diode having a low withstand voltage can be used instead of a diode having a high withstand voltage, and there is an advantage that integration is possible.

In addition, the third diode 530 may be implemented as an IC internal parasitic diode formed parasitic between the drain and GND of the second MOSFET 420 when the sequential current driver 400 is integrated. 18 or less, the position of the fourth diode 540 is not directly connected to the capacitor 300 to which a high voltage is applied, but moves to the source position of the second MOSFET 420, and is directly connected to the capacitor 300 When the driving MOSFET (the second MOSFET 420) is integrated, the separate third diode 530 may be omitted because it is naturally formed when the driving MOSFET (the second MOSFET 420) is integrated.

19 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 18 according to another embodiment of the present invention, a current mirror is added between the first MOSFET 410 of the sequential current driver 400 and the light emitting diode to make the current flowing through the light emitting diode equal. perform the function

20 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 18 according to another embodiment of the present invention, the output terminal is connected to the gate terminal of the first MOSFET 410 to the sequential current driver 400, the first operational amplifier 430, and 2 This shows a circuit in which driving characteristics are improved by further including a second operational amplifier 440 having an output terminal connected to the gate terminal of the MOSFET 420 .

21 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 20 according to another embodiment of the present invention, a current flowing in the light emitting diode is measured by adding a current mirror 600 between the first MOSFET 410 of the sequential current driving unit 400 and the light emitting diode. perform the same function.

22 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in FIG. 18 according to the present embodiment, a third MOSFET 450 and a fourth MOSFET 460 are additionally included in the sequential current driving unit 400 to configure a cascode circuit to improve operating characteristics. It is a diagram showing the circuit.

23 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 22 according to another embodiment of the present invention, a current mirror 600 is added between the first MOSFET 410 and the third MOSFET 450 of the sequential current control unit in the form of a cascode to emit light. It performs the function of making the current flowing through the diode equal.

24 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown in FIG. 22 , it _{is a diagram showing a circuit in which the position of D 4} is moved from the source of the second MOSFET 420 to the source of the fourth MOSFET 460 according to the present embodiment. The role of D4 is to prevent the current flowing in the reverse direction in the section in which the capacitor drives the light emitting diode, and performs the same function as that connected to the source of the first MOSFET as shown in FIG. 22 . In addition, when the first MOSFET and the second MOSFET are directly connected as shown in FIG. 24, the operation characteristics of the sequential current driver become simpler.

25 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in FIG. 24 according to the present embodiment, by adding a current mirror 600 between the first MOSFET and the third MOSFET, it is a diagram showing a circuit that performs the function of making the driving current of the light emitting diode the same.

26 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 22 according to another embodiment of the present invention, the output terminal is connected to the gate terminal of the first MOSFET 410 to the sequential current driver 400, the first operational amplifier 430, the second 2 This shows a circuit in which driving characteristics are improved by further including a second operational amplifier 440 having an output terminal connected to the gate terminal of the MOSFET 420 .

27 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in FIG. 26 according to the present embodiment, by adding a current mirror 600 between the first MOSFET and the third MOSFET, it is a diagram showing a circuit that performs a function of making the driving current of the light emitting diode the same.

28 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in the drawing of FIG. 24 according to another embodiment of the present invention, the output terminal is connected to the gate terminal of the first MOSFET 410 to the sequential current driver 400, the first operational amplifier 430, and 2 This shows a circuit in which driving characteristics are improved by further including a second operational amplifier 440 having an output terminal connected to the gate terminal of the MOSFET 420 .

29 is a circuit diagram of an AC direct-connected light emitting diode driving device including an LED driving capacitor according to another embodiment of the present invention. As shown, in FIG. 28 according to the present embodiment, by adding a current mirror 600 between the first MOSFET and the third MOSFET, it is a diagram showing a circuit that performs a function of making the driving current of the light emitting diode the same.

30A to 30E are diagrams illustrating a circuit that can be used as a current mirror according to an embodiment of the present invention. The current mirror used in the present invention is a circuit that generates a current proportional to the sequential current driver current and drives the light emitting diode with the sum of the sequential driving current and the proportional current generated by the current mirror. Although only the diagram using PMOS is shown, the same configuration is possible with a PNP transistor.

The present invention described above is not limited to the above-described embodiments and drawings, and it is common knowledge in the field to which the present invention pertains that any number of substitutions, changes and modifications are possible without departing from the technical spirit of the present invention. It will be clear to those who have

100: rectifying unit 200: light emitting diode unit
300: capacitor 400: sequential current driver
500: charge/discharge control unit

Claims (14)

delete delete a rectifying unit for receiving and rectifying an AC power voltage;
a light emitting diode unit receiving the rectified voltage from the rectifying unit and emitting light;
a capacitor for driving the light emitting diode unit during the discharging period while repeating a charging period, a sustain period, a discharge period, and a sustain period according to a preset period;
A sequential current driving unit including a switching element for controlling a path of a current flowing through the light emitting diode unit and the capacitor according to different input voltage levels, and a resistor connected to the switching element and a ground terminal to control a driving current of the switching element Wow;
a first diode connected between the light emitting diode unit and the first end of the capacitor to form a current path from the light emitting diode unit to the capacitor; and the capacitor connected between the light emitting diode unit and the first end of the capacitor A second diode forming a current path from the light emitting diode unit, and a third diode connected between a ground terminal and a second end of the capacitor to form a current path from the switching element to the capacitor; and
The switching element is
a first MOSFET having a drain terminal connected between the light emitting diode unit and the first diode and a source terminal connected to the resistor;
a second MOSFET having a drain terminal connected to a path connected to the capacitor and a source terminal connected to the resistor,
The charge/discharge control unit,
and a fourth diode connected to the capacitor and the current path of the second MOSFET and preventing current from flowing from the first MOSFET to the second MOSFET during the discharging period;
The fourth diode has an anode connected to a second terminal of the capacitor and a cathode connected to a drain terminal of the second MOSFET. 4. The method of claim 3,
The fourth diode has an anode connected to a source terminal of the second MOSFET and a cathode connected to the resistor. 4. The method of claim 3,
and a current mirror positioned on a path connecting the cathode end of the light emitting diode unit and the drain terminal of the first MOSFET, and further comprising a current mirror for increasing the light emitting diode driving current. 4. The method of claim 3,
The third diode is a parasitic diode formed parasitic between the drain and GND of the second MOSFET when the sequential current driver is integrated. 6. The method according to any one of claims 3 to 5,
The light emitting diode driving device further comprising a parallel capacitor connected in parallel with the light emitting diode unit. 6. The method according to any one of claims 3 to 5,
The sequential current driving unit,
a first operational amplifier having an output terminal connected to the gate terminal of the first MOSFET;
The light emitting diode driving device further comprising a second operational amplifier having an output terminal connected to the gate terminal of the second MOSFET. 6. The method according to any one of claims 3 to 5,
The sequential current driving unit,
a first cascode element connected in series to the drain terminal of the first MOSFET to which a bias voltage is applied to a third terminal or a gate terminal;
and a second cascode element connected in series to the drain terminal of the second MOSFET to which a bias voltage is applied to a third stage or a gate terminal. 10. The method of claim 9,
The sequential current driving unit,
a first operational amplifier having an output terminal connected to the gate terminal of the first MOSFET;
The light emitting diode driving device further comprising a second operational amplifier having an output terminal connected to the gate terminal of the second MOSFET. a rectifying unit for receiving and rectifying an AC power voltage;
a light emitting diode unit receiving the rectified voltage from the rectifying unit and emitting light;
a capacitor for driving the light emitting diode unit during the discharging period while repeating a charging period, a sustain period, a discharge period, and a sustain period according to a preset period;
A sequential current driving unit including a switching element for controlling a path of a current flowing through the light emitting diode unit and the capacitor according to different input voltage levels, and a resistor connected to the switching element and a ground terminal to control a driving current of the switching element Wow;
a first diode connected between the light emitting diode unit and the first end of the capacitor to form a current path from the light emitting diode unit to the capacitor; and the capacitor connected between the light emitting diode unit and the first end of the capacitor A second diode forming a current path from the light emitting diode unit, and a third diode connected between a ground terminal and a second end of the capacitor to form a current path from the switching element to the capacitor; and
The sequential current driving unit,
a first MOSFET for controlling a path of a current flowing through the light emitting diode unit according to different input voltage levels;
a second MOSFET for controlling the path of the current flowing through the capacitor;
a third MOSFET for bias in which a bias voltage is applied as a gate to the drain terminal of the first MOSFET;
a fourth MOSFET for bias in which a bias voltage is applied as a gate to the drain terminal of the second MOSFET;
The charge/discharge control unit,
and a fourth diode having an anode connected to a source terminal of the fourth MOSFET and a cathode connected to a drain terminal of the second MOSFET. 12. The method of claim 11,
The sequential current driving unit,
a first operational amplifier having an output terminal connected to the gate terminal of the first MOSFET;
The light emitting diode driving device further comprising a second operational amplifier having an output terminal connected to the gate terminal of the second MOSFET. 12. The method of claim 11,
The switching element is
A light emitting diode driving device comprising any one of a Baltic Juice Terminal (BJT), an Insulated Gate Bipolar Transistor (IGBT), and a MOSFET. 12. The method of claim 11,
The third diode is a parasitic diode formed parasitic between the drain and GND of the fourth MOSFET when the sequential current driver is integrated.

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