WO2017043756A1

WO2017043756A1 - Device and method for driving power factor compensated-type led

Info

Publication number: WO2017043756A1
Application number: PCT/KR2016/007843
Authority: WO
Inventors: 유수근; 김봉철
Original assignee: 유수근; (주)옵토마인드
Priority date: 2015-09-08
Filing date: 2016-07-19
Publication date: 2017-03-16
Also published as: KR101796431B1; KR20170029999A

Abstract

Disclosed are a device and a method for driving a power factor compensated-type LED using LC. The present embodiment relates to a device and a method for driving a power factor compensated-type LED. More particularly, the present invention relates to a device and a method for driving an LED, which drive an LED by compensating for a power factor and controlling a current using a current control unit.

Description

Power factor compensation LED driver and driving method

This embodiment relates to a power factor correcting LED driver and a driving method.

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

A power supply device is required to drive the LED (Light Emitting Diode). LED power supplies are divided into Switching Mode Power Supply (SMPS) and AC Direct.

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

However, the SMPS method has a problem in that failures such as a smoothing capacitor or a powerFET for switching occur frequently among components. Some of the causes of such failures are known to be caused by operating conditions such as temperature rise due to LED heating and continuous use for a long time. In addition, some of the reasons for the failure of the SMPS method may be because the LED light is a device directly connected to a power line in a factory or outdoors, and is used in a severe disturbance environment such as surge. LED light fixtures are very demanding compared to other electronic devices with requirements such as efficiency, power factor, Total Harmonic Distortion (THD) and lifetime.

On the other hand, in order to solve these disadvantages, an AC direct type LED power supply has been recently developed. AC direct eliminates high-speed switching operations and provides several levels of constant current control from full-wave rectified pulsating voltage to power LEDs while satisfying power factor and THD conditions. The AC direct method does not use high-speed switching PowerFETs or smoothing capacitors, resulting in long life due to fewer failures.

However, the AC direct method does not solve the problem of output power fluctuations caused by fluctuations in input voltage. In the AC direct method, when the input voltage fluctuates by 10%, the output power fluctuates by 10%. In addition, the AC direct method has a disadvantage in that a large amount of heat is generated by overloading the constant current device when the input voltage is increased, and the driving IC is destroyed when the input voltage is suddenly changed. Therefore, the AC direct method should be limited to within 10% of the fluctuation condition of the input voltage used.

In the AC direct system, since the output power is pulse, flicker appears as it is in the shape of the pulse voltage. In order to alleviate this flicker problem, a method of using a smoothing capacitor has been tried. However, the use of the smoothing capacitor shortens the life time of the LED lamp. The AC direct method supplies a pulse current to the LED, so the ratio of light conversion to power is lower than that of the SMPS method, and thus there is a limit in increasing the total light efficiency (Lumen per Watt) as the SMPS method.

As another method, there has recently been a passive power factor correction type LED driving device using only LC. Since the passive power factor correction driving device compensates for the power factor using only an inductor and a capacitor, which are energy storage elements, there is almost no loss, so the power-to-light conversion efficiency is very high. Inductors and film capacitors used in passive drives are more resistant to failures or unexpected breakdowns, and therefore longer than other drive lifetimes. However, the passive power factor correction type LED driving device has a problem in that the output power fluctuation due to the change in the input voltage is very large as in the AC direct method.

This embodiment aims to provide a power factor correction type constant current LED driver using LC that eliminates the disadvantages of output variation while taking advantage of the passive driver.

In addition, to improve the power factor of the LED driving device to improve the energy efficiency using L and C passive energy storage device, and to provide a LED driving device to remove the fluctuation of the output power by supplying a controlled current to the LED using the current control unit. The purpose is to.

According to an aspect of the present embodiment, in the LED driving device for supplying current to the LED (Light Emitting Diode) module, it is connected to the input power source, using a LC (Inductor Capacitor) to compensate for the phase difference between the voltage and the input current PFC (Power Factor Correction) control unit; A rectifier connected to the PFC controller and converting the input voltage into a direct current pulse voltage; A capacitor connected to the rectifier, the capacitor storing or supplying a charge corresponding to a difference between the current rectified in the rectifier and a current flowing through the LED module; And a current control unit controlling a current flowing through the LED module in a switching mode.

According to an embodiment of the present invention, in the LED driving current controller for controlling the current flowing in the LED module in the LED (Light Emitting Diode) driving device including a rectifier, a switch and a capacitor, for opening and closing the current flowing through the LED module switch; An inductor for linearly increasing the current flowing to the LED module when the switch is turned on and linearly decreasing the current flowing to the LED module when the switch is turned 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 current flowing through the LED module; A comparator for comparing the voltage across the current sense resistor with a reference voltage Vref1 and transferring the voltage to one side delay inverter; And a gate driver connected to the one side delay time inverter to open and close the switch.

According to the present embodiment, the energy efficiency is improved by using L and C, which are passive energy storage devices, to control the power factor of the LED driving device, and to control the current supplied to the LED, thereby eliminating the variation of the output power due to the variation of the input voltage. It works.

1 is a conceptual block diagram of an LED driving apparatus according to an embodiment.

2 is a circuit diagram of an LED driving apparatus according to an embodiment.

3 is a circuit diagram when the current control unit of the LED driving apparatus according to the embodiment is not operated (in the case where the input voltage Vi is small).

FIG. 4 shows a signal waveform diagram of each part when the current control part of the LED driving device of FIG. 3 is not operated (in the case where the input voltage Vi is small).

5 illustrates an operation of a circuit in a case where the bridge diode of the LED driving device is Off and On in accordance with an embodiment.

FIG. 6 shows a signal waveform diagram of each part when the current control part of the LED driving device of FIG. 5 operates (in the case where the input voltage Vi is large).

7 is a circuit diagram illustrating an implementation of a linear mode current control unit according to an embodiment.

8 is a circuit diagram illustrating an implementation of a switching mode current control unit according to an embodiment.

9 is a waveform diagram of each part of the switching mode current controller of FIG. 8.

10 is a circuit diagram of a one-side delay time inverter according to an embodiment.

FIG. 11 is a waveform diagram of each part of the one-side delay time inverter of FIG. 10.

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

In adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even though they are shown in different drawings. In describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, in describing the component of this invention, terms, such as 1st, 2nd, A, B, (a), (b), can be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but there may be another configuration between each component. It is to be understood that the elements may be "connected", "coupled" or "connected".

1 is 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 power factor correction (PFC) control unit 120, a rectifier 130, a capacitor 140, a current control unit 150, and an LED module 160.

The input power source 110 supplies AC power to the LED driving device 100.

The PFC control unit 120 is used to prevent the phase difference between the voltage and the current from cos0 due to a device having a power input configuration in which a capacitor exists such as a switching mode power supply (SMPS).

Power factor (PF) refers to the cos difference of phase time in the flow of the waveform of voltage and current of the input power source 110. The power factor is expressed as in Equation 1.

Where is the phase difference between voltage and current.

The power factor is cos0 = 1 if the phase of the input voltage and input current match, and cos90 = 0 for complete mismatch. When describing the power factor of the actual product, only the result value calculated as in Equation 1 is expressed, for example, 0.9.

The PFC control unit 120 is divided into a passive type and an active type.

Passive PFCs use capacitors or inductors to add or remove reactive current by a pre-measured reactive portion at relatively variable loads.

Active PFC simulates power factor using FETs, diodes, additional double-voltage rectifiers and capacitors to model the load as a linear load. Since the load is accurately modeled so as not to be affected by the fluctuation of the power supply voltage 110, the power factor comes out over a predetermined reference, for example, 0.95. However, active PFC has a loss in power conversion process. Active PFC repeats charging and discharging when power is input, eliminating or adding reactive power due to phase difference, making the load appear as a resistive load.

The rectifier 130 converts an AC input voltage into a DC pulse voltage using a bridge diode. The bridge diode refers to a bridge circuit connecting four diodes. The bridge diode outputs the same polarity voltage regardless of the polarity of the input voltage. The rectifier 130 generates a voltage loss by a turn-on voltage of the diode, for example, 0.7 to 1.0 V.

The capacitor 140 stores the current corresponding to the difference if the output current of the bridge diode is greater than the current flowing through the LED module. On the other hand, when the output current of the bridge diode is less than the current flowing through the LED module, the capacitor 140 supplies a current corresponding to the difference to the LED module.

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

2 is 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 controller 150, and an LED module 160.

The input power source 110 is connected to one terminal of the inductor L1 to provide an AC voltage. The inductor L1 serves not only to primarily limit the current input to the LED, but also serves as a PFC that compensates for the power factor with the capacitor C1.

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

The circuit of FIG. 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.

3 is a circuit diagram when the current control unit of the LED driving apparatus according to the embodiment is not operated (in the case where the input voltage Vi is small). When the input voltage Vi is small, the current control unit 150 becomes a resistance (ideally 0 Ohm) smaller than the predetermined resistance. Therefore, the voltage Vd at both ends of 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 a signal waveform diagram of each part when the current control part of the LED driving device of FIG. 3 is not operated (in the case where the input voltage Vi is small). As shown in (a) of FIG. 4, the input voltage Vi has a positive value and increases from the time point T0. At this time, the voltage of the capacitor C1 starts with the value -Vf which was the voltage when the bridge diode 220 was turned on during the negative half period of the previous cycle.

The operation of the circuit will be described below with reference to FIGS. 5 and 4.

In the waveform diagram sections T1 and T2 of FIG. 4A, the bridge diode 220 is turned off, and only the inductor L1 and the capacitor C1 exist as shown in FIG. 5A. It works as a circuit. Here, the initial voltage of the capacitor C1 is -Vf. At this time, the voltage at both ends of the inductor L1 takes Vi-Vc, and the current of the inductor increases with the slope of (Vi-Vc) / L1. Since the bridge diode 220 is turned off, all of the current in the inductor L1 flows into the capacitor C1, thereby increasing Vc.

In the period T1, since Vi-Vc has a positive value, the inductor current Ii increases with a positive slope. At the end of the period T1, the value of Vi-Vc becomes zero, at which time the inductor current Ii becomes the maximum point. Since the inductor current (Ii) is positive in the interval T2, the voltage of the capacitor (C1) continues to increase. However, the inductor current Ii decreases because the voltage Vi-Vc across the inductor becomes negative. As soon as Vc continues to increase and becomes greater than the voltage Vd (= Vf) across the capacitor C2, the bridge diode 220 is turned on so that current flows to the capacitor C2 and the LED. The intervals for this operation are T3, T4, T5 and T0. During this period, Vd remains constant at the LED forward voltage Vf. Since capacitor C1 is connected, Vc continues to be maintained at Vf.

The operation of the circuit in the section where the bridge diode 220 is turned on is as shown in FIG. From this point on, the voltage across the inductor runs across Vi-Vd. At this time, since Vd is Vf, the 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 increases again. 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 a residual section in which a positive current flows even though the input voltage Vi is changed to negative.

The position or size of each section may be changed according to the values of the inductor L1 and the capacitor C1, and thus the waveform of the input current Ii may be changed. Therefore, by adjusting the values of the inductor L1 and the capacitor C1, the input current can be moved forward or to the ground with respect to the input voltage. In addition, the shape of the input current waveform can be adjusted to control total harmonic distortion (THD). Therefore, power factor compensation can be performed.

The value of the inductor L1 should be a valid value at a power supply frequency of 50 to 60 Hz, and a few hundred mH bands may be appropriate but not necessarily limited thereto. From the section T0, the input voltage Vi operates in the same way as the positive section in the negative section, and only the direction (sign) is changed.

The input current Ii is a current Idi passed by the bridge diode 220 except for the hatched portion of FIG. 4B, and this current I is the same as that of FIG. 4C. The input current Idi of the diode 220 is a full-wave rectified current Id by the bridge diode 220, and this current Id is shown in Fig. 4 (d). Becomes the current supplied to the LED.

When 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 retains the form of FIG. As the full-wave rectified current Id increases, the current Iled flowing in the LED increases, and the LED becomes brighter. That is, output fluctuations occur due to voltage fluctuations.

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

FIG. 6 is a signal waveform diagram of each part when the current control unit 150 of the LED driving device of FIG. 5 operates (when the input voltage Vi is large). Unlike FIG. 4, Vd is not constant as Vf, and Vd varies around the average voltage Vdavg. FIG. 6C shows a full wave rectified current Id waveform diagram. In FIG. 6, the section T0 is the last cycle of all cycles, the bridge diode 220 is turned off in the sections T1 and T2, and the bridge diode 220 is turned on in the sections T3, T4, T5, and T0.

In the period T1, a voltage of 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 into the capacitor C1, thereby increasing the voltage Vc across the capacitor C1. When Vc is higher than the input voltage (Vi), the voltage across the inductor goes from zero to negative. Therefore, the inductor current Ii decreases temporarily (T2 period). Vc continues to increase because the inductor current Ii is still positive in the period T2, and the bridge diode 220 is turned on as soon as Vc becomes higher than the voltage Vd at both ends of C2. From then on, C1 and C2 are connected to make Vc and Vd the same.

The bridge diode 220 is turned off during the periods T1 and T2, and the capacitor C2 is discharged with the current Ilim set toward the LED, so that Vd decreases. In the sections T3 and T4, the periods up to the time point t6 are decreased because the flowing current Id of the bridge diode 220 is smaller than the set current Ilim, and the flowing current Id of the bridge diode 220 is set. The voltage Vd increases from the time t6 which becomes larger than the current Ilim. When the period T5 becomes higher than the input voltage Vi, the inductor current Ii decreases again with the slope of (Vi-Vd) / L1. Vd increases until time t7 at which the current of the inductor becomes smaller than the set current Ilim, and Vd decreases after time t7 because the LED continues to discharge. This operation is repeated in the next cycle where the input voltage Vi becomes negative.

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

When the LED driver 100 adjusts the values of the inductor L1 and the capacitor C1 to predetermined values, the power factor and the THD may be adjusted. The value of the capacitor C2 is preferably set to be equal to or greater than a value at which a voltage at which the current controller 150 can operate is maintained. In other words, if the value of the capacitor C2 is set to be equal to or greater than the value that is not discharged to maintain the voltage at which the current control unit 150 can operate, from the time t7 which is the period in which the capacitor C2 discharges to the time t6 of the next cycle do.

7 is a circuit diagram illustrating an implementation 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. A drain of the FET Q2 is connected to the LED module, and a 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.

Using this method, when Vd increases, Vs increases, so that the limit current Ilim flowing to the LED side can be made constant. However, Vd-Vf is applied across FET Q2, and the total power of FET Q2 is (Vd-Vf) * Ilim, which is consumed by heat. In other words, as the input voltage Vi increases, the loss increases, so it is not recommended to use this method when the output power is large. However, this disadvantage can be solved by the switching mode current controller.

8 is a circuit diagram illustrating an implementation of a switching mode current control unit according to an embodiment. The switching mode current controller 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.

If the input voltage Vi is greater than a constant voltage so that the average value of the full-wave rectified current Id is greater than or equal to the voltage larger than the output current Io flowing to the LED, the LED current Iled even if the input voltage Vi becomes larger. In order to constantly flow), the switching mode current control unit 840 is used.

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

When the output of the comparator 820 becomes high, the output of the comparator 820 becomes low immediately. When the output of the comparator 820 becomes low, the inverter 810 delays a predetermined time Td. The output goes high. Here, the high of the output of the comparator 820 may be a rising edge, and the furnace may be a falling edge.

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

When the input voltage Vi is greater than or equal to the current source operating voltage, the operation of the switching mode current controller 840 will be described. When the switch Q1 is initially turned off, since Io does not flow, 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. After the predetermined delay time Td, the output of the one-sided delay inverter 810 becomes high, and the switch Q1 is turned on through 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 turns off, and the voltage Vd of the capacitor C2 across the LED and the inductor Ls becomes Takes The voltage across the inductor Ls is Vd-Vf minus the total forward voltage Vf of the LED, and the current Iled of the inductor Ls increases linearly with a slope of (Vd-Vf) / Ls. .

When the switch Q1 is on, Iled = Io, and the voltage Iled * Rs (= Io * Rs) across the resistor Rs increases linearly. As soon as the voltage across resistor Rs continues to increase and becomes greater than Vref1, the output of comparator 820 goes high. At this time, the output of the one-side delay time inverter 810 becomes low without a 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-side delay time inverter 810 drives the gate driver 830 so that the switch Q1 is turned on again.

The reflux diode Dw is turned on while the switch Q1 is turned off for a predetermined delay time Td of the one-side delay time inverter 810. The inductor current flows back to the freewheeling diode. The forward voltage Vf of the LED is reversed across the inductor Ls to decrease the slope of -Vf / Ls. The amount of decreasing current is determined by Td, the inductor Ls value, and the Vf value.

9 is a waveform diagram of each part of the switching mode current controller 840 of FIG. 8. 9A is a waveform of the product of current Iled flowing through the LED multiplied by the resistance value Rs. 9B is a waveform of the output of the gate driver 830. 9C is a waveform of the drain voltage of the switch Q1. The current flowing through the resistor Rs is as shown in FIG.

Io = Iled in the section where switch Q1 is on and 0 in the section where it is off. Since the maximum value of the current Iled flowing in the LED becomes Vref1 / Rs, and the minimum value Imin decreases while the switch Q1 is turned off, Equation 2 is obtained.

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 Iled _avg of the current Iled flowing in the LED can be expressed as in Equation 3.

Iled _avg becomes the limiting current Ilim of the current source. As shown in Equation 3, the limit current is independent of 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. Constant current drive is irrelevant.

Note that unlike the linear mode, the average current of the output current Io decreases as the input voltage Vi increases and Vd increases. However, the current (Iled) flowing through the LED is kept constant. In the linear mode current control unit 710, when Vd increases, heat is consumed from the current source by the increase. However, since the switching mode current controller 840 temporarily stores magnetic energy in the inductor Ls and supplies the stored energy when the switch Q1 is turned off, the switch Q1, the inductor Ls, and the freewheeling diode. If (Dw) is ideal, there is no loss at all. Therefore, even if the input voltage Vi increases, both input power and output power remain unchanged. In the linear mode, when the input voltage Vi increases, the input power increases because the voltage output across the current source increases due to the increased heat loss even though the power output to the LED is unchanged.

When the input voltage Vi is lowered and Vd is lowered, the voltage across the resistor Rs does not reach the reference voltage Vref1 and the switch Q1 remains in the on state. In addition, no voltage is applied to both ends of the inductor Ls, and the input current Id flows to the LEDs so that the operation of the current source is stopped, and the current controller 840 simply operates with a small resistance Rs.

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

FIG. 11 is a waveform diagram of each part of the one-side delay time inverter of FIG. 10. If input A is low, switch Qd is turned off, capacitor Cd is charged from Vref2 through resistor Rd, and voltage Vcd of capacitor Cd increases to the value of Vref2. Since Vref3 is set lower than Vref2, the output B goes high.

As shown in Fig. 11A, when the input A is changed from low to high, the switch Qd is turned on, the capacitor Cd is discharged, and Vcd becomes 0V. Since Vcd is lower than Vref3, the output B becomes low. When the input A is inverted to low in the high state, the switch Qd is turned off. From this point on, Vcd starts charging via resistor Rd from Vref2. The waveform at the time of charging of the Vcd is shown in Fig. 11B. 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.

The comparator 802 outputs high when Vcd increases and becomes larger than the non-inverting terminal reference voltage Vref3 of the comparator 802. Therefore, as shown in (c) of FIG. 11, the output B becomes high after a predetermined time Td delay at the time t2 when the input A becomes low. Td is a solution of equation (5).

If Td is designed in a range sufficiently smaller than the time constant Rd * Cd, the above equation can be solved by approximating Equation 6 by Taylor series.

Therefore, Td is represented by Equation 7.

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

In the above, Td can be arbitrarily set by the combination of the values of the resistor Rd, the capacitor Cd, Vref3 and Vref2 in FIG. 10.

The above description is merely illustrative of the technical idea of the present embodiment, and those skilled in the art to which the present embodiment belongs may make various modifications and changes without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment but to describe the present invention, 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 interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiment.

As described above, according to the exemplary embodiments of the present invention, the power factor is compensated for using the LC, and at the same time, it serves as a EMI filter and a surge protection. By controlling the LED current, there is an effect of improving the efficiency, power factor and EMI characteristics of the LED driver.

120: PFC controller 130: rectifier

150: current control unit 220: bridge diode

710: linear mode current control unit 810: one-sided delay time inverter

830: gate driver 840: switch mode current controller

1010: reference voltage charging circuit

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority under No. 119 (a) (35 USC § 119 (a)) of the Patent Application No. 10-2015-0127286 filed with Korea on September 08, 2015. All content is incorporated by reference in this patent application. In addition, this patent application claims priority to countries other than the United States for the same reasons, all of which are incorporated herein by reference.

Claims

In the LED driver for supplying current to the LED (Light Emitting Diode) module,

A power factor correction (PFC) control unit connected to an input power source and compensating a phase difference between a voltage and an input current using an inductor capacitor (LC);

A rectifier connected to the PFC controller and converting the input voltage into a direct current pulse voltage;

A capacitor connected to the rectifier, the capacitor storing or supplying a charge corresponding to a difference between the current rectified in the rectifier and a current flowing through the LED module; And

Current control unit for controlling the current flowing in the LED module in the switching mode (Switching Mode)

LED drive device comprising a.
The method of claim 1,

The current control unit,

A switch for opening and closing a current flowing through the LED module;

An inductor for linearly increasing the current flowing to the LED module when the switch is turned on and linearly decreasing the current flowing to the LED module when the switch is turned 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 current flowing through the LED module;

A comparator for outputting an output signal comparing the voltages of both ends of the current sensing resistor with 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 at only one edge (rising edge or falling edge) with respect to the output signal received; And

A gate driver connected to an output of the one-side delay time inverter to open and close the switch according to the received inversion signal;

LED drive device comprising a.
The method of claim 2,

The limit value (Iled avg ) of the current flowing through the LED,

As in the following equation,

LED, characterized in that it is determined by the resistance (Rs), inductor (Ls), LED forward voltage (Vf), delay time (Td), reference voltage (Vref1) and constant (1/2) independent of the input voltage Drive system.
The method of claim 2,

The one side delay time inverter,

A switch connected to the comparator and the gate driver and configured to receive an output of the comparator and to open and close the output;

A charging unit connected to the switch and charging the capacitor through a reference voltage Vref2 and a resistor; And

A comparator connected to the charging unit and inputting the comparator to the gate driver in comparison with the reference voltage Vref2 and the capacitor charging voltage

LED drive device comprising a.
The method of claim 4, wherein

The delay time is,

As in the following equation,

LED driving device, characterized in that determined by the resistance (Rd), capacitor (Cd) and the ratio of the reference voltage (Vref3 / Vref2).
The method of claim 1,

The PFC control unit,

One end of the input power and one end of the inductor L1 are connected in series, and the other end of the inductor L1 and one end of the capacitor C1 are connected, and the other end of the capacitor C1 is connected to the other end of the input power. LED drive device characterized in that.
The method of claim 1,

The rectifier is a LED driving device, characterized in that using a bridge diode.
The method of claim 1,

The current control unit,

If the input current is less than the set current of the current control unit, LED drive device, characterized in that to operate simply with a small resistance.
The method of claim 8,

LED driving device, characterized in that the voltage across the capacitor is limited to the forward voltage of the LED module.
The method of claim 1,

The current control unit,

And when the input current is greater than the set current of the current controller, the average voltage across the capacitor is changed to be equal to the set limit value of the average current rectified by the rectifier and the current flowing through the LED.
The method of claim 10,

And an average voltage across the capacitor increases and decreases according to the magnitude of the voltage of the input power source.
The method of claim 1,

The current control unit,

LED driving device, characterized in that for controlling the current flowing in the LED module in a linear mode (Linear Mode).
The method of claim 12,

The current control unit,

A FET connected to the LED module and a drain;

A linear mode voltage sensing resistor connected to a source of the FET to sense current flowing through 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

LED drive device comprising a.
The method of claim 13,

The current control unit,

Even if the voltage across the capacitor increases, the drain and source voltage of the FET and the voltage across the voltage sensing resistor increases by an increase to control the current flowing through the LED module to a set current value.
In the LED driving current controller for controlling the current flowing in the LED module in the LED (Light Emitting Diode) driving device including a rectifier, a switch and a capacitor,

A switch for opening and closing a current flowing through the LED module;

An inductor for linearly increasing the current flowing to the LED module when the switch is turned on and linearly decreasing the current flowing to the LED module when the switch is turned 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 current flowing through the LED module;

A comparator for outputting an output signal comparing the voltages of both ends of the current sensing resistor with 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 at only one edge (rising edge or falling edge) with respect to the output signal received; And

A gate driver connected to an output of the one-side delay time inverter to open and close the switch according to the received inversion signal;

LED drive current controller, characterized in that it comprises.
The method of claim 15,

The one side delay time inverter,

An inverter switch connected to the comparator and the gate driver and configured to open and close an output of the comparator;

A charging unit connected to the inverter switch to charge an inverter capacitor through a reference voltage Vref2 and an inverter resistance; And

An inverter comparator connected to the charging unit and inputting to the gate driver in comparison with the reference voltage Vref2 and the charging voltage of the inverter capacitor

LED drive current controller, characterized in that it comprises.
The method of claim 15,

The current controller for driving the LED, characterized in that for increasing the delay time to reduce the current flowing through the LED module.
Compensating for the phase difference from the input power to the input current using an LC (Inductor Capacitor);

Converting the input power into a direct current;

Storing a charge corresponding to a difference between the current and a current flowing through a light emitting diode (LED) module or supplying a current to the LED module; And

Controlling the current flowing through the LED module in a switching mode.

LED driving method comprising a.
The method of claim 19,

Opening and closing a current flowing through the LED module;

Linearly increasing or decreasing a current flowing in the LED module;

Returning a current flowing through the LED module; And

Detecting the current flowing through the LED module to open and close the current flowing through the LED module with a delay time

LED driving method comprising a.