KR20170029999A - LED Driver and Driving Method for Power Factor Correction - Google Patents

Abstract

Disclosed are a device and a method for driving an LED for power factor compensation using LC, which remove an output variation. An embodiment of the present invention relates to the device and the method for driving an LED for power factor compensation. More specifically, the present invention relates to the device and the method for driving an LED, which drive an LED by compensating a power factor and controlling current through a current control unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a power factor correction type LED driving device,

The present embodiment relates to a power factor compensating LED driving apparatus and a driving method. More particularly, the present invention relates to an LED driving apparatus and a driving method for driving an LED by compensating a power factor and controlling a current using a current control unit.

The contents described below merely provide background information related to the present embodiment and do not constitute the prior art.

A power supply is required to drive the LED (Light Emitting Diode). There are two types of LED power devices: Switching Mode Power Supply (SMPS) and AC Direct.

The SMPS method is a device for supplying DC power from an AC power source and is widely used in most electronic devices. Since the LED device is basically a device that operates by receiving DC power, it is convenient and efficient to supply the DC power to the LED.

However, SMPS has a problem that frequent failures such as a smoothing capacitor and a power FET for switching are included in the components. Some of the causes of failures are known to be caused by operating environments such as temperature rise due to LED heat generation and continuous use for a long time. LED light is a device directly connected to a power line in a factory or outdoors, so it seems to be used in a disturbance environment such as a surge. LED lamps are very demanding in terms of efficiency, power factor, total harmonic distortion (THD) and lifetime in comparison to other electronic devices.

In order to solve these drawbacks, recently, an AC direct type LED power supply device has been developed. AC Direct eliminates high-speed switching operation and controls the constant current in several steps from full-wave rectified pulsating voltage to supply power to LED while satisfying power factor condition and THD condition. The AC direct method does not use a power FET or a smoothing capacitor for high-speed switching.

AC direct method has not solved the problem of output power fluctuation due to input voltage variation. When the input voltage fluctuates by 10%, the output power fluctuates by about 10%. In addition, when the input voltage is high, the constant current device is overloaded and generates a lot of heat. In the case of abrupt change of the input voltage, the driving IC is destroyed, and the fluctuation condition of the input voltage to be used should be limited within 10%.

In the AC direct method, since the output power is a pulsating current, the flicker appears in the form of pulsating voltage. In order to alleviate this flicker problem, a method of solving the problem by using a smoothing capacitor is attempted, but the use of the smoothing capacitor shortens the lifetime of the LED lamp. Since the AC direct method supplies pulsed power to the LEDs, the power conversion ratio is lower than that of the SMPS method, so there is a limit to increase the total light efficiency (Lumen per Watt) by the SMPS method.

As another method, a passive type power factor correction type LED driving device using only LC has recently been developed. This passive-type power factor compensation type driving apparatus uses power factor inductors and capacitors alone to compensate the power factor, so there is little loss and power-to-light conversion efficiency is very high. The inductors and film capacitors used in passive drives are strong against breakdowns and unexpected breakdowns, so the life of the drive is long in preparation for other methods.

The present embodiment has an object to provide a constant-current-power-factor-compensated constant-current LED driving apparatus using an LC that eliminates a disadvantage in output fluctuation while taking advantage of a passive driving apparatus.

Also, an LED driving device is provided to increase the energy efficiency by using passive energy reservoirs L and C for power factor compensation of the LED driving device, and to control the current using the current control part to supply the LED to the output power variation The purpose is to do.

According to an aspect of the present invention, there is provided an LED driving apparatus for supplying a current to an LED (Light Emitting Diode) module, the LED driving apparatus being connected to an input power source and compensating for a phase difference between a voltage and an input current by using an LC (Inductor Capacitor) A PFC (Power Factor Correction) control unit; A rectifier connected to the PFC controller to convert the input voltage into a DC pulse voltage; A capacitor connected to the rectifying unit and storing or supplying a charge equal to a difference between a current rectified by the rectifying unit and a current flowing through the LED module; And a current controller for controlling a current flowing through the LED module in a switching mode.

According to an embodiment of the present invention, there is provided an LED driving current controller for controlling a current flowing in an LED module in an LED (Light Emitting Diode) driving apparatus including a rectifier, a switch and a capacitor, switch; An inductor for linearly increasing a current flowing through the LED module when the switch is on and for reducing a current flowing through the LED module linearly when the switch is off; A free wheeling diode for returning a current flowing in the inductor when the switch is turned off; A current sensing resistor connected to a source of the switch and sensing a current flowing in the LED module; A comparator for comparing the voltage across the current sensing resistor with a reference voltage Vref1 and delivering it to a one-side delay time inverter; And a gate driver connected to the one side delay time inverter for opening and closing the switch.

According to an embodiment of the present invention, a method of compensating a phase difference between an input voltage and an input current using an LC (Inductor Capacitor); Converting the input power to a direct current; Storing electric charges corresponding to the difference between the current and a current flowing in an LED (Light Emitting Diode) module or supplying current to the LED module; And controlling a current flowing in the LED module in a switching mode.

According to this embodiment, energy efficiency is improved by using L and C, which are passive energy storage devices, to compensate the power factor of the LED driving device, and the current supplied to the LED is controlled to remove the fluctuation of the output power according to the variation of the input voltage It is effective.

1 shows a conceptual block diagram of an LED driving apparatus according to an embodiment.
2 shows a circuit diagram of an LED driving apparatus according to an embodiment.
Fig. 3 shows a circuit diagram when the current control unit of the LED driving apparatus according to the embodiment does not operate (the input voltage Vi is small).
Fig. 4 shows signal waveforms of respective parts when the current control unit of the LED driving apparatus of Fig. 3 does not operate (the input voltage Vi is small).
5 shows the operation of the circuit when the bridge diode of the LED driving apparatus according to the embodiment is off and when it is on.
Fig. 6 shows a signal waveform diagram of each part when the current control section of the LED driving apparatus of Fig. 5 is operated (when the input voltage Vi is large).
FIG. 7 shows an implementation circuit diagram of a linear mode current control unit according to an embodiment.
FIG. 8 shows an implementation circuit diagram of a switching mode current control unit according to an embodiment.
9 shows a waveform diagram of each part of the switching mode current control unit of Fig.
10 shows a circuit diagram of a one-sided delay time inverter according to one embodiment.
11 shows waveforms of respective parts of the one-sided delay time inverter of Fig.

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

In adding reference numerals to the constituent elements of the drawings, it is to be noted that the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), (b) and the like can be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

1 shows a conceptual block diagram of an LED driving apparatus according to an embodiment. The LED driving apparatus 100 includes an input power source 110, a PFC controller 120, a rectifier 130, a capacitor 140, a current controller 150, and an LED module 160.

The input power supply 110 supplies AC power to the LED driving apparatus 100.

The PFC controller 120 is used to prevent the phase difference between the voltage and the current from moving away from cos0 due to a device having a power input configuration in which a capacitor exists, such as an SMPS (Switching Mode Power Supply).

Power Factor (PF) means the cosine difference of the phase time in the flow of the voltage and current waveforms of the input power source 110. The power factor is expressed by Equation (1).

Where ∮ is the phase difference between voltage and current.

If the input voltage and the input current are in phase, then the power factor is cos0 = 1 and cos90 = 0 for perfect mismatch. When expressing the power factor of an actual product, it is indicated by only the result of calculation as shown in Equation (1).

PFC is divided into passive type and active type.

Passive PFCs use capacitors or inductors to add or remove reactive current for a pre-measured ineffect at relatively low load.

The active PFC simulates the power factor using an FET, a diode, an additional voltage rectifier circuit and a capacitor to model the load as a linear load. Since the load is modeled precisely so as not to be influenced by fluctuations of the power supply voltage 110, the power factor is 0.95 or more. However, active PFCs lose power during the power conversion process. The active PFC repeats charging and discharging when the power is input, eliminating or adding the reactive power due to the phase difference so that the load looks like a resistive load.

The rectifier 130 converts the AC input voltage into a DC ripple voltage using a bridge diode. A bridge diode is a bridge circuit that connects four diodes. The bridge diode outputs the same polarity voltage irrespective of the polarity of the input voltage. The turn-on voltage of the diode, that is, the voltage loss by 0.7 to 1.0 V, occurs.

If the output current of the bridge diode is larger than the current flowing in the LED module, the capacitor 140 stores the current of the difference in the capacitor 140. On the other hand, if the output current of the bridge diode is smaller than the current flowing in the LED module, a current corresponding to the difference is supplied from the capacitor 140 to the LED module.

The current controller 150 controls the current supplied to the LED module. The current controller 150 may be implemented by a linear mode or a switching mode. This will be described in detail with reference to FIGS. 7 and 8, respectively.

2 shows a circuit diagram of an LED driving apparatus according to an embodiment. The LED driving apparatus 200 includes an input power source 110, an inductor L1 and a capacitor C1, a bridge diode 220, a capacitor C2, a current control unit 150 and an LED module 160. [

The input power supply 110 is connected to one terminal of the inductor L1 to provide an AC voltage. The inductor L1 serves not only to limit the current input to the LEDs, but also to function as a PFC to compensate the power factor together with the capacitor C1.

The bridge diode 220 functions to full-wave rectify the AC power. The capacitor C2 temporarily stores the energy when the full-wave rectified current Id is larger than the current Iled flowing through the LED, and the full-wave rectified current Id is smaller than the current Iled flowing through the LED In this case, it supplies the stored energy to the LED.

The circuit of Figure 2 can operate in two cases. One is a case where the input voltage Vi is small and the input current is small, and the full-wave rectified current Id passed by the rectifying action of the bridge diode is smaller than the set current Ilim of the current source Is. The other is a case where the input voltage Vi is large and the full-wave rectified current Id is larger than the set current Ilim. When the input voltage Vi is small, the circuit of Fig. 2 is equivalent to the circuit of Fig.

Fig. 3 shows a circuit diagram when the current control unit of the LED driving apparatus according to the embodiment does not operate (the input voltage Vi is small). When the input voltage Vi is small, the current controller 150 simply becomes a small resistor (ideally 0 Ohm). Therefore, the voltage across the capacitor (C2) is limited to the forward voltage (Vf) of the LED module. The operation in this case will be described with reference to the waveform diagram of Fig.

Fig. 4 shows signal waveforms of respective parts when the current control unit of the LED driving apparatus of Fig. 3 does not operate (the input voltage Vi is small). As shown in FIG. 4 (a), the input voltage Vi increases from a time point T0 with a positive value. At this time, the voltage of the capacitor C1 starts with a value of -Vf which was the voltage when the bridge diode 220 is turned on during the negative half period of the previous cycle.

5 shows the operation of the circuit when the bridge diode of the LED driving apparatus according to the embodiment is off and when it is on.

Hereinafter, the operation of the circuit will be described with reference to FIG. 5 and FIG.

4 (a), the bridge diode 220 is turned off and the input stage circuit includes only the inductor L1 and the capacitor C1 as shown in FIG. 5 (a) Circuit. The initial voltage of the capacitor C1 is -Vf. At this time, the voltage at both ends of the inductor L1 becomes Vi-Vc, and the current of the inductor increases at a slope of (Vi-Vc) / L1. Since the bridge diode 220 is off, all the current of the inductor L1 flows to the capacitor C1. Therefore, Vc also increases.

In section T1, since Vi-Vc has a positive value, the inductor current Ii has a positive slope and increases. At the end of the interval T1, the value of Vi-Vc becomes 0, and the inductor current (Ii) becomes the maximum point at this time. In the subsequent section T2, since the inductor current Ii is positive, the voltage of the capacitor C1 continuously increases. However, since the voltage Vi-Vc across the inductor becomes negative, the inductor current Ii decreases. As soon as Vc continues to increase to become greater than the voltage Vd (= Vf) across the capacitor C2, the bridge diode 220 turns on and current flows to the capacitor C2 and the LED. The sections that perform this operation are T3, T4, T5, and T0. During this interval, Vd remains constant at the LED forward voltage (Vf). Since the capacitor C1 is connected, Vc is also maintained at Vf.

The operation of the circuit in the section where the bridge diode 220 is on is shown in Fig. 5 (b). From this point on, the voltage across the inductor is taken to Vi-Vd. At this time, since Vd is Vf, a voltage of Vi-Vf is applied. In the period T3, Vi-Vf becomes negative and the inductor current Ii decreases. In the period T4, Vi-Vf becomes positive and the inductor current Ii again increases. At the end of the period T4, as the input voltage Vi decreases, Vi-Vf becomes negative and the inductor current Ii rapidly decreases. The section T0 is the residual section in which the positive current flows even when the input voltage Vi is changed to negative.

The position and the size of each section can be changed according to the value of the inductor L1 and the capacitor C1 and thus the waveform of the input current Ii can also be changed. Therefore, by adjusting the values of inductor (L1) and capacitor (C1), the input current can be moved forward or backward with respect to the input voltage. In addition, the shape of the input current waveform can be adjusted to adjust the THD (Total Harmonic Distortion). Therefore, it is possible to compensate the power factor.

The value of the inductor L1 must be a valid value at a power frequency of 50 to 60 Hz, and approximately several hundreds of mH are appropriate, but are not necessarily limited thereto. From the interval T0, the input voltage Vi operates in the same manner as the positive interval in the negative interval, but only in the direction (sign).

The input current Ii is the current Idi passed through the bridge diode 220 except for the shaded portion of FIG. 4 (b), as shown in FIG. 4 (c). The input current Idi of the bridge diode 220 is the same as the current Id of the full-wave rectified by the bridge diode 220 as shown in (d) of FIG. The full-wave rectified current Id becomes a current supplied to the LED.

As the input voltage Vi increases, the amplitude of the inductor current Ii also increases, and thus the average current of the full-wave rectified current Id also increases. Of course, the shape maintains the shape of FIG. 4 (d). When the full-wave rectified current Id increases, the current Iled flowing through the LED increases, and the LED becomes brighter. That is, the output fluctuation occurs due to the voltage fluctuation.

The case where the input voltage Vi is large will also be described with reference to FIG. When the input voltage Vi increases and the current of the full-wave rectified current Id exceeds the set current Ilim of the current control unit 150 of FIG. 2, only the Ilim flows to the LED side, and the remaining current flows to the capacitor C2 ). Therefore, the voltage Vd across the capacitor C2 increases. When Vd increases, the period T4 decreases in the waveform diagram of FIG. 4A, and the inductor current Ii decreases while the voltage Vi-Vd across the inductor L1 during this period decreases. Therefore, an average voltage of Vd is formed at a voltage at which the average current Id is equal to Ilim. Therefore, even if the input voltage Vi increases, the output current of the LED is maintained at Ilim.

Fig. 6 shows signal waveforms of respective parts when the current controller 150 of the LED driving apparatus of Fig. 5 operates (when the input voltage Vi is large). Unlike FIG. 4, Vd is not constant at Vf, and Vd fluctuates around the average voltage (Vdavg). 6 (c) shows the waveform of the full-wave rectified current (Id). 6, the period T0 is the last cycle of the previous cycle, and the bridge diode 220 is turned off during the periods T1 and T2, and the bridge diode 220 is turned on during the periods T3, T4, T5, and T0.

At interval T1, the voltage across Vi-Vc is applied across the inductor. At this time, since Vi-Vc is positive, the inductor current Ii of the inductor L1 increases with a slope of (Vi-Vc) / L1. At this time, all the current flows to the capacitor C1, thereby increasing the voltage Vc across the capacitor C1. When Vc becomes higher than the input voltage (Vi), the voltage across the inductor becomes zero and turns negative. Therefore, the inductor current Ii is temporarily reduced (T2 period). Vc continues to increase because the inductor current Ii continues to be positive in the period T2, and the instant bridge diode 220 is turned on when Vc becomes higher than the voltage Vd at both ends of C2. From this point, C1 and C2 are connected and Vc and Vd become equal.

Since the bridge diode 220 is turned off during the periods T1 and T2 and the capacitor C2 is discharged with the current Ilim set to the LED side, Vd is decreased. Since the current Id flowing through the bridge diode 220 is smaller than the current Ilim of the bridge T3 and the current flowing through the bridge T4 during the period t4, the current Id of the bridge diode 220 is set The voltage Vd increases from time t6, which is greater than current Ilim. The inductor current Ii decreases again with a slope of (Vi-Vd) / L1 when the period T5 in which Vd is higher than the input voltage Vi. Vd increases until time t7 when the current of the inductor becomes smaller than the set current Ilim, and Vd decreases after time t7 because the discharge continues with the LED. This operation is repeated even in the next cycle in which the input voltage Vi becomes negative.

The average voltage Vdavg of Vd is not fixed and the average voltage Vdavg increases when the input voltage Vi increases and the average voltage Vdavg decreases when the input voltage Vi decreases. The average voltage Vdavg of Vd is shifted so that the average current of the full-wave rectified current Id is equal to the value of Ilim so that the current flowing through the LED is kept constant. If the input voltage Vi becomes lower and the average voltage Vdavg must be lower than Vf of the LED, Is can no longer operate as a current source. As shown in FIG. 3, it operates with a small resistance (ideally 0 Ohm).

The power factor and THD can be adjusted by adjusting the values of the inductor (L1) and capacitor (C1) to appropriate values. The value of the capacitor C2 may be set to a value which is not discharged so as to maintain the voltage at which the current controller 150 can operate from the time t7 in which the capacitor C2 is discharged to the time t6 of the next cycle.

FIG. 7 shows an implementation circuit diagram of a linear mode current control unit according to an embodiment. The linear mode current controller 710 includes a resistor Rb, a zener diode Vz, a FET Q2, and a resistor Rs. The drain of the FET Q2 is connected to the LED module and the resistor Rb is connected between Vd and the gate of the FET Q2 to provide a bias current to the zener diode Vz. A zener diode Vz for applying a constant voltage to the gate of the FET Q2 and a resistor Rs for setting the LED current are connected to the source terminal of the FET Q2. At this time, the limit current Ilim is (Vz-Vgs) / Rs.

With this method, when Vd becomes high, Vs becomes high, and the limit current Ilim flowing on the LED side can be made constant. However, Vd-Vf is applied to both ends of the FET Q2, and the total power of the FET Q2 becomes (Vd-Vf) * Ilim, which is all consumed as heat. That is, as the input voltage Vi increases, the loss increases. Therefore, when the output power is large, it is preferable not to use this method. However, this disadvantage can be solved by the switching mode current controller.

FIG. 8 shows an implementation circuit diagram of a switching mode current control unit according to an embodiment. The switching mode current control unit 840 includes a switch Q1, a diode Dw, an inductor Ls, a resistor Rs, a comparator 820, a gate driver 830 and a one-side delay time inverter 810.

When the input voltage Vi becomes larger than a constant voltage and the average value of the full-wave rectified current Id becomes larger than the voltage greater than the output current Io flowing to the LED, even if the input voltage Vi becomes larger, The switching mode current controller 840 is used.

The switch Q1 is a transistor for a current switch, and an NMOS transistor is used here, but an NPN transistor can be used instead of the NMOS transistor. The resistor Rs is a current sensing resistor. The comparator 820 monitors the difference between the sensed voltage Rs * Io and the reference value Vref1.

The one-sided delay time inverter 810 immediately makes the output low when the output of the comparator 820 becomes high and delays the predetermined time Td when the output of the comparator 820 goes low. The output goes high.

The gate driver 830 amplifies the output voltage of the one-side delay time inverter 810 and drives the gate of the switch Q1. The inductor Ls serves to linearly increase the current flowing through the LED when the switch Q1 is turned on and to linearly decrease the current when the switch Q1 is turned off. The diode Dw is a free wheeling diode that returns the current flowing in the inductor Ls when the switch Q1 is turned off.

The operation when the input voltage Vi is equal to or higher than the current source operating voltage will be described. When the switch Q1 is initially turned off, Io does not flow, so that the voltage Rs * Io across Rs is lower than the predetermined comparison voltage Vref1. At this time, the output of the comparator 820 becomes low. The output of the one-side delay time inverter 810 becomes high after the predetermined delay time Td and the switch Q1 is turned on via the gate driver 830. [ When the switch Q1 is turned on, the drain voltage Vdrain of the switch Q1 becomes 0 V, the diode Dw is turned off, and the voltage Vd of the capacitor C2 is supplied to both ends of the LED and the inductor Ls It takes. The voltage across the inductor Ls becomes Vd-Vf minus the total forward voltage Vf of the LED at Vd and the current Iled of the inductor Ls linearly increases with a slope of (Vd-Vf) / Ls .

At this time, Iled = Io (when the switch Q1 is on) and the voltage Iled * Rs (= Io * Rs) across the resistor Rs linearly increases. The output of the instantaneous comparator 820 becomes high when the voltage across the resistor Rs continues to increase and becomes larger than Vref1. At this time, the output of the one-side delay time inverter 810 becomes low without delay time and the switch Q1 is turned off. When the switch Q1 is turned off, the voltage across the resistor Rs becomes 0 V, and the output of the comparator 820 becomes low. When the output of the comparator 820 becomes low, the one-side delay time inverter 810 outputs high after a predetermined delay time Td. The output of the one-sided delay time inverter 810 drives the gate driver 830 so that the switch Q1 is turned on again.

While the switch Q1 is turned off for the predetermined delay time Td of the one-side delay time inverter 810, the reflux diode Dw is turned on. The inductor current flows back to the reflux diode. The forward voltage Vf of the LED is reversely applied to both ends of the inductor Ls and decreases at a slope of -Vf / Ls. The amount of the decreasing current is determined by Td, the inductor Ls value, and the Vf value.

9 shows waveforms of respective parts of the switching mode current controller 840 of FIG. 9 (a) is a waveform of a current Iled flowing through an LED multiplied by a resistance value Rs. (b) is a waveform of the output of the gate driver 830. Fig. (c) is a waveform of the drain voltage of the switch Q1. The current flowing through the resistor Rs is as shown in (d).

Io = Iled in the period in which the switch Q1 is on, and 0 in the off-period. The maximum value of the current Iled flowing through the LED is Vref1 / Rs, and the minimum value Imin decreases while the switch Q1 is off.

는 수학식 3과 같이 나타낼 수 있다.Where Rs is the resistance value, Ls is the inductor value, Vf is the forward voltage of the LED module, Td is the delay time, and Vref1 is the reference voltage. Therefore, the average current of the current Iled flowing through the LED

Can be expressed by Equation (3).

This is the limiting current Ilim of the current source. As shown in Equation 3, since the limiting current is not related to the input voltage, Rs is the resistance value, Ls is the inductor value, Vf is the forward voltage of the LED module, Td is the delay time and Vref1 is the reference voltage. The constant current drive is irrelevant.

Note that unlike in the linear mode, when the input voltage Vi increases and Vd increases, the average current of the output current Io decreases. However, the current Ile flowing through the LED remains constant. In the linear mode current control unit 710, as Vd increases, the current source consumes as much heat as the increase. However, since the switching mode current control unit 840 temporarily stores the energy in the inductor Ls as magnetic energy and supplies the stored energy when the switch Q1 is turned off, the switch Q1 and the inductor Ls, (Dw) is ideal, there is no loss at all. Therefore, even if the input voltage Vi increases, both the input power and the output power are not changed. In the linear mode, when the input voltage Vi increases, the input power increases because the voltage across the current source increases and the heat loss increases even though the power output from the LED does not fluctuate.

When the input voltage Vi is lowered and Vd is lowered, the voltage across the resistor Rs does not reach the reference voltage Vref1, so that the switch Q1 is continuously turned on. Further, no voltage is applied to both ends of the inductor Ls, and all the input current Id flows into the LEDs to stop the operation of the current source, and the current control unit simply operates with a small resistance Rs.

10 shows a circuit diagram of a one-sided delay time inverter according to one embodiment. One side delay time inverter 810 includes a switch Qd, a resistor Rd, a capacitor Cd and a comparator 802. When the input A is high, the voltage Vcd becomes 0 V. When the input A is low, the reference voltage charging circuit 1010 charges the capacitor Cd through the resistor Rd to the voltage Vref2. . When Vcd is charged and reaches Vref3, the output (B) of the comparator 802 goes high again. When the input A changes to low, the output is one side delay time inverter 810 that goes high with a delay time Td. Of course, the delay time Td can be adjusted for the resistor Rd, the capacitor Cd, Vref2 and Vref3.

11 shows waveforms of respective parts of the one-sided delay time inverter of Fig. When the input A is low, the switch Qd is turned off and the capacitor Cd is charged from Vref2 through the resistor Rd so that the voltage Vcd of the capacitor Cd increases to the value of Vref2. Since Vref3 is set lower than Vref2, the output B becomes high.

11A, when the input A is changed from low to high, the switch Qd is turned on, the capacitor Cd is discharged, and Vcd is 0 V. Since Vcd is lower than Vref3, the output (B) becomes low. When the input A is inverted from the high state to the low level, the switch Qd is turned off. From this time, Vcd starts charging from Vref2 through the resistor Rd. The waveform upon charge of Vcd is shown in Fig. 11 (b). This charging waveform becomes a time function as shown in Equation (4).

Where Rd is the resistance value, Cd is the capacitor value, and Vref2 is the reference voltage.

When Vcd increases and becomes larger than the non-inverting terminal reference voltage Vref3 of the comparator 802, the comparator 802 outputs a high level. Therefore, the output (B) becomes high after a predetermined time Td delay at time t2 when the input (A) becomes low as shown in (c) of FIG. Td is the solution of equation (5).

If Td is designed in a range that is sufficiently smaller than the time constant Rd * Cd, then the above equation can be solved by approximating it with the Taylor series as shown in equation (6).

Therefore, Td is expressed by Equation (7).

Where Rd is the resistance value, Cd is the capacitor value, and Vref2 and Vref3 are constant reference voltages.

Thus, Td can be arbitrarily set by a combination of the values of the resistor Rd, the capacitor Cd, Vref3, and Vref2 in Fig.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

As described above, according to the embodiments of the present invention, the power factor is compensated using the LC, and the role of EMI filter and surge protection are performed. The efficiency of the LED driving device, the power factor and the EMI characteristics are improved by controlling the LED current.

120: PFC controller 130:
150: current control unit 220: bridge diode
710: Linear mode current controller 810: One side delay time inverter
830: Gate driver 840: Switch mode current controller
1010: Reference voltage charging circuit

Claims (19)

An LED driving apparatus for supplying current to an LED (Light Emitting Diode) module,
A PFC (Power Factor Correction) controller connected to the input power source for compensating a phase difference between a voltage and an input current by using an LC (Inductor Capacitor);
A rectifier connected to the PFC controller to convert the input voltage into a DC pulse voltage;
A capacitor connected to the rectifying unit and storing or supplying a charge equal to a difference between a current rectified by the rectifying unit and a current flowing through the LED module; And
A current controller for controlling current flowing in the LED module in a switching mode;
The LED driving device comprising: The method according to claim 1,
The current control unit includes:
A switch for opening / closing a current flowing in the LED module;
An inductor for linearly increasing a current flowing through the LED module when the switch is on and for reducing a current flowing through the LED module linearly when the switch is off;
A free wheeling diode for returning a current flowing in the inductor when the switch is turned off;
A current sensing resistor connected to a source of the switch and sensing a current flowing in the LED module;
A comparator for outputting an output signal obtained by comparing a voltage between both ends of the current sensing resistor and a reference voltage Vref1;
A one-side delay time inverter connected to the output of the comparator and outputting an inverted inverted signal having a delay time only at one edge (rising edge or falling edge) with respect to the received output signal; And
And a gate driver connected to the output of the one-side delay time inverter for opening and closing the switch in accordance with the inverted signal received
The LED driving device comprising: 3. The method of claim 2,
The limit value of the current flowing through the LED

)this,
As shown in the following equation,

Wherein the output voltage is determined by a resistor Rs, an inductor Ls, a forward voltage Vf of the LED, a delay time Td, a reference voltage Vref1 and a constant 1/2, which are independent of the input voltage. Driving device. 3. The method of claim 2,
The one-sided delay time inverter includes:
A switch connected to the comparator and the gate driver for receiving an output of the comparator to open and close the comparator;
A charging unit connected to the switch for charging the capacitor through a reference voltage Vref2 and a resistor; And
A comparator connected to the charging unit for comparing the reference voltage Vref2 with the capacitor charging voltage and inputting the comparison voltage to the gate driver,
The LED driving device comprising: 5. The method of claim 4,
The delay time may be,
As shown in the following equation,

Is determined by a ratio (Vref3 / Vref2) of a resistor (Rd), a capacitor (Cd), and a reference voltage. The method according to claim 1,
The PFC controller,
One end of the input power source and one end of the inductor L1 are connected in series and the other end of the inductor L1 is connected to one end of the capacitor C1 and the other end of the capacitor C1 is connected to the other end of the input power source And the LED driving device. The method according to claim 1,
Wherein the rectifying unit uses a bridge diode. The method according to claim 1,
The current control unit includes:
And when the input current is smaller than the current set by the current control unit, the LED driving unit operates with a small resistance. 9. The method of claim 8,
Wherein a voltage across the capacitor is limited to a forward voltage of the LED module. The method according to claim 1,
The current control unit includes:
Wherein an average voltage across the capacitor is varied to be equal to a predetermined limit value of an average current rectified by the rectifying unit and a current flowing through the LED when the input current is greater than the set current of the current control unit. 11. The method of claim 10,
Wherein an average voltage across the capacitor is increased or decreased according to a magnitude of a voltage of the input power source. The method according to claim 1,
The current control unit includes:
And controls a current flowing in the LED module in a linear mode. 13. The method of claim 12,
The current control unit includes:
An FET connected to the LED module and a drain;
A linear mode voltage sensing resistor connected to a source of the FET to sense a current flowing in the LED module;
A zener diode connected to the gate of the FET to set a gate voltage; And
A bias resistor for supplying a bias current of the Zener diode
The LED driving device comprising: 14. The method of claim 13,
The current control unit includes:
Wherein a voltage across the drain and the source voltage of the FET and a voltage across the voltage sensing resistor increase by an increment even if the voltage across the capacitor increases, thereby controlling the current flowing through the LED module to a predetermined current value. 1. A LED driving current controller for controlling a current flowing in an LED module in an LED (Light Emitting Diode) driving device including a rectifying part, a switch and a capacitor,
A switch for opening / closing a current flowing in the LED module;
An inductor for linearly increasing a current flowing through the LED module when the switch is on and for reducing a current flowing through the LED module linearly when the switch is off;
A free wheeling diode for returning a current flowing in the inductor when the switch is turned off;
A current sensing resistor connected to a source of the switch and sensing a current flowing in the LED module;
A comparator for outputting an output signal obtained by comparing a voltage between both ends of the current sensing resistor and a reference voltage Vref1; And
A one-side delay time inverter connected to the output of the comparator and outputting an inverted inverted signal having a delay time only at one edge (rising edge or falling edge) with respect to the received output signal; And
And a gate driver connected to the output of the one-side delay time inverter for opening and closing the switch in accordance with the inverted signal received
And a current controller for driving the LED. 16. The method of claim 15,
The one-sided delay time inverter includes:
An inverter switch connected to the comparator and the gate driver for receiving and opening the output of the comparator;
A charging unit connected to the inverter switch for charging the inverter capacitor through a reference voltage Vref2 and an inverter resistance; And
And an inverter comparator connected to the charging unit for comparing the reference voltage Vref2 with the charging voltage of the inverter capacitor and inputting the comparison voltage to the gate driver,
And a current controller for driving the LED. 16. The method of claim 15,
And the current flowing to the LED module decreases as the delay time increases. Compensating an input voltage from an input power source by using an LC (Inductor Capacitor) to compensate a phase difference between the input voltage and an input current;
Converting the input power to a direct current;
Storing electric charges corresponding to the difference between the current and a current flowing in an LED (Light Emitting Diode) module or supplying current to the LED module; And
And controlling the current flowing in the LED module in the switching mode
The LED driving method comprising the steps of: 20. The method of claim 19,
Opening and closing a current flowing in the LED module;
Linearly increasing or decreasing a current flowing through the LED module;
Returning a current flowing through the LED module; And
Detecting a current flowing through the LED module and opening / closing a current flowing through the LED module with a delay time
The LED driving method comprising the steps of:

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