KR101478782B1 - LED Driving Circuit for AC Driving and Dimming Based on Constant Current of Sine Wave - Google Patents

Abstract

The present invention provides an AC (Alternating Current) power source suitable for harmonic regulation and power factor regulation, enabling direct driving and dimming of an LED (Light Emitting Diode), and a simple circuit , An LED driving circuit capable of driving even at a low AC input, and capable of driving with excellent flicker characteristics by keeping the current constant even when the input AC voltage fluctuates.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC driving and a dimming circuit,

The present invention relates to an LED driving circuit, which is capable of directly driving and dimming an LED (Light Emitting Diode) with an AC (Alternating Current) power source of a sinusoidal current suitable for harmonic regulation and power factor regulation, The present invention relates to an LED driving circuit that can be driven with a low AC input without any increase of the AC voltage and can maintain a constant current even when the input AC voltage fluctuates, so that the flicker characteristic can be excellent.

Generally, in a conventional LED driving circuit, an AC power supply voltage is applied to two input terminals of a bridge diode, and a current rectified by a bridge diode is controlled to drive LEDs provided in an LED module to emit light. Korean Patent Application Nos. 10-2010-0056623, 10-2010-0056683, and the like can be referred to as related arts.

In addition, Korean Patent Application No. 10-2011-0113891 (LED multi-stage drive control device) discloses a circuit for driving the LED module as shown in FIG. 1, in order to stop the flow of the auxiliary currents (i _Q2 , i _Q3 , i _Q4 ) when the main current i _Q1 flows according to the change of the input power source V _ac , R _off20 , R _off30 , R _off40 were used and D ₁ , R _off31 , and D ₂ , R _off42 were used to stop the flow of the remaining auxiliary currents (i _Q3 , i _Q4 ) when the auxiliary current i _Q2 flowed, and the auxiliary current i _Q3 D ₃ , R off ₄₁ was used to stop the flow of the remaining auxiliary current i _Q4 when flowing. In addition, the sensing resistors R _sen1 , R _sen2 , R _sen3 , and R _sen4 are used to sense the main current and the auxiliary current. The detailed operation procedure can be referred to the patent document.

However, in such a conventional LED driving circuit, although the number of current levels of four stages is illustrated in FIG. 1, in order to increase the number of current levels to improve the light efficiency and the harmonic characteristic, There is a problem that the number of parts such as diodes and resistors for cutting off the flow of auxiliary current exponentially increases.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide an AC (alternating current) AC power source capable of driving and dimming an LED (Light Emitting Diode) Provides an LED driving circuit that can be driven with low AC input using a simple circuit without a large increase in the number of parts, and can keep the current constant even when the input AC voltage fluctuates, thereby achieving excellent flicker characteristics I have to.

According to an aspect of the present invention, there is provided an LED driving circuit including a plurality of LEDs connected in series to a plurality of light emitting diodes And a control circuit for controlling each current flowing from the negative terminal connection point to the ground terminal using each three-terminal switch, wherein the plurality of LEDs In order to sequentially emit one or more LEDs on the positive terminal side of the LED and the last LED on the negative terminal side and sequentially turn off in the reverse order, the control circuit controls the one or more LEDs And a main current switch connected to the last LED, wherein the auxiliary current switch and the main current switch One of the circuits for turning off the corresponding LED and turning off the other terminal of the auxiliary current switch and the auxiliary current switch, And the contact is connected to a resistor through which a current flows when the main current switch is turned on.

As the main current switch and the at least one auxiliary current three-terminal switch, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or a bipolar transistor may be used.

A metal-oxide-semiconductor field-effect transistor (MOSFET), a bipolar transistor, or a shunt regulator is used as a three-terminal switch for controlling or turning off the current of the main current switch, (Metal-Oxide-Semiconductor Field-Effect Transistor), or a bipolar transistor, can be used as a three-terminal switch for controlling or turning off the current of the switch.

The circuit for controlling the auxiliary current switch can be made of the same circuit without a diode.

A circuit including N (N is a natural number) photocouplers is connected to a circuit including a resistor whose one terminal is connected to another terminal of the main current switch to which the corresponding LED is connected, and each switch connected to the photocoupler is turned on And a plurality of dimming steps corresponding to on / off combinations of the switches can be performed by changing a resistance connected to the resistors connected to the other terminals.

The LED driving circuit is characterized by driving the LED module having the plurality of LEDs formed of DC LED elements or the LED module having the plurality of LEDs formed of AC LED elements.

According to the LED driving circuit of the present invention, it is possible to drive an LED (Light Emitting Diode) even with an AC input of a low sine wave current by using a simple circuit without a large increase in the number of parts, The current can be kept constant even when the AC voltage fluctuates and the flicker characteristic can be improved.

1 is a view for explaining a conventional LED driving circuit.
2 is a diagram for explaining an LED driving circuit according to an embodiment of the present invention.
FIG. 3 is a diagram for explaining the relationship between the main current and the auxiliary currents (i _Q1 , i _Q2 , i _Q3 , i _Q4 ) according to the change of the input power source (V _ac ) of FIG.
Fig. 4 shows an embodiment in which the four-stage circuit of Fig. 2 has three stages.
FIG. 5 is a diagram for explaining the relationship between the main current and the auxiliary currents (i _Q1 , i _Q2 , i _Q3 ) according to the change of the input power source V _ac of FIG.
6 is an embodiment in which a dimming circuit is added to the circuit of FIG.
Figure 7 shows the experimental results for the circuit of Figure 2;
Figure 8 shows the experimental results for the circuit of Figure 4;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

2 is a diagram for explaining an LED driving circuit according to an embodiment of the present invention.

2, an LED driving circuit according to an exemplary embodiment of the present invention includes an LED module 110 having two or more LEDs (Light Emitting Diodes) D ₁ , D ₂ , D ₃ , and D ₄ connected in series , A rectifying section 10 and other control circuits.

The rectifying part 10 (for example, a bridge diode) receives AC power Vac and supplies DC power, that is, rectified to a positive voltage, to the LED module 110. In the bridge diode, two sets of two diodes connected in series are connected in parallel, the series connection connection points are the input terminals of the AC power supply Vac, and the parallel connection connection points are the output terminals.

Each of the three-terminal switches Q ₁ , Q ₂ , Q ₃ and Q ₄ connected to the respective negative terminals of the series-connected LEDs D ₁ , D ₂ , D ₃ and D ₄ of the LED module 110 (I _Q1 , i _Q2 , i _Q3 , i _Q4 ) flowing from each negative terminal connection point of the LEDs to the ground terminal to control the rise and fall of the power rectified by the rectification section 10 One or more LEDs (D ₁ , D ₂ , D ₃ ) on the positive terminal side of the LEDs of the LED module 110 and the last LED (D ₄ ) on the negative terminal side sequentially emit light in the reverse order, . Here, the three-terminal switches Q ₁ , Q ₂ , Q ₃ and Q ₄ may be MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or bipolar transistors. The switch q ₁ connected to the gate of Q ₁ among the circuits for controlling off of the three-terminal switches Q ₁ , Q ₂ , Q ₃ and Q ₄ may also be composed of a MOSFET or a bipolar transistor, The switches q ₂ , q ₃ , and q ₄ connected to the respective gates of the three-terminal switches Q ₂ , Q ₃ , and Q ₄ may be formed of a MOSFET, a bipolar transistor, or a shunt regulator (see U _{1 in} FIG. 4).

2 and 4, the LED module 110 includes four LEDs D ₁ , D ₂ , D ₃ , and D ₄ , and the LED module 210 includes three LEDs the two LED (D _1, D _2, D ₃₎ can be driven in such a manner as to to to drive all LED modules, for example described as including, but more than two series-connected LED to, It is also possible to improve the harmonic characteristics by including more LEDs such as 5, 6, ... in the LED module and increasing the number of current control levels driving those LEDs.

In particular, the LED driving circuit of the present invention can drive an LED module even at a low input of a sine wave current (Vac) by using a simple circuit without increasing the number of parts even if the number of current control levels is increased, (dimming) is possible, and the current is kept constant even when the input AC voltage fluctuates, so that the flicker characteristic can be improved.

₂ , each of the three-terminal switches Q ₁ , Q ₂ , and Q 3 connected to the negative terminals of the series-connected LEDs D ₁ , D ₂ , D ₃ , and D ₄ of the LED module 110, ₃ and Q ₄ are connected to an auxiliary current switch (not shown) connected to one or more LEDs (D ₁ , D ₂ , D ₃ ), which are sequentially turned on in accordance with the rise of the power rectified by the rectifying part _{(Q 4, Q 3, Q} 2) and a last LED and main current switches (Q ₁₎ for coupled to (D _4).

The switches of the same control circuit _{(Q 1, Q 2, Q} 3, Q 4) and according to the control of other circuits, a switch for a second current _{(Q 4, Q 3, Q} 2) switch (Q ₁ for the main current ) is turned on in order that can emit light to the LED connected to each in that order, the switch for the main current switches (Q ₁₎ and the auxiliary current for _{(Q 4, Q 3, Q} 2) is turned off in turn coupled to respective The LEDs can be turned off in that order (in the reverse order of the light emission).

To this end, as shown in Figure 2, each of the secondary current switch (Q _4, Q _3, Q ₂₎ circuit for turning off the terminal and the secondary current switch (Q _4, Q _3, Q ₂₎ for the LED opposite the (switch Q ₄ , Q ₃ , and Q ₂ ) are connected to the same point, which is a resistor through which current flows when the main current switch Q ₁ is turned on (for example, R connected to _gs1, R _s1, R _sen1, R _sen2, etc.) under the control.

In this way, each of the secondary current switch (Q _4, Q _3, Q ₂₎ circuit for controlling the (switch Q _4, Q _3, a circuit coupled to the gate terminal of Q _2, respectively), both without a diode as in the prior art the same circuit The circuit is simplified without increasing the number of components even if the number of current control levels is increased by increasing the number of LEDs of the LED module 110. [

For example, for an LED module 110 consisting of n LEDs, the input voltage Vac is positive and the voltage increases to produce a forward voltage of 1/4 * n * The input current passes through the diode BD ₁ of the rectifying section 10 and reaches 1/4 of the LED module 110 (V _F ) (V _F is the LED forward voltage) (Eg, D ₁ ) to drive MOSFET Q ₄ through resistor R _B , zener diodes Z _DB and R _B4 , and current begins to flow through MOSFET Q ₄ (D ₁ radiation). At this time, the current flowing through the sensing resistors (R _sen2 + R _sen1 ) turns into a voltage, which drives the gate of MOSFET q ₄ through R _off4 . Of course, this time q voltage applied to the gates of _four is determined by the distribution voltage of the R _off4 and R _gs4 resistance when the voltage is driven to q _4, predetermined as the secondary current i _Q4 is (a) of Figure 3 flowing through the MOSFET Q ₄ .

That is, when sensing the primary current (i _Q1) R _sen1 are used, and when sensing a second current (i _{Q2, Q3} i, i _Q4) (R _sen2 + R _sen1 ) is used, so that the auxiliary current and the main current can be separated to increase the degree of design freedom. For simplicity, it is also possible to remove R _sen2 and unify it to R _sen1 .

When the input voltage Vac is positive and the voltage further increases and becomes larger than 2/4 forward voltage (2/4 * n * V _F ) with respect to the n LED modules 110 ), The input current passes through the diode BD ₁ of the rectifying section 10 and passes through the half of the LED module 110 (D ₁ , D ₂ ) to start current flow through the MOSFET Q ₃ that has already been turned on (D ₁ , D ₂ radiation). At this time, the current flowing through the sensing resistors (R _sen2 + R _sen1 ) is converted into a voltage, which drives the gate of q ₃ through R _off3 . Of course, this time q voltage applied to the gate of the ₃ R _off3 and R _gs3 are determined by the distribution voltage of the resistor when the voltage is driven to q _3, predetermined as the secondary current i _Q3 is (a) of Figure 3 flowing through the MOSFET Q ₃ Lt; / RTI > At this time, the R _off3 and R _gs3 resistance values are designed such that the current of i _Q3 is larger than the current of i _Q4 so that the sensing resistances R _sen2 + R _sen1 ), and this design will control the auxiliary current i _Q3 to be constant, while at the same time turning on the MOSFET q ₄ through R _off4 (the gate voltage of q ₄ is R _off4 , R _gs4 resistance), and the operation of the auxiliary switch Q ₄ is stopped (0ff). As a result, the flow of the current i _Q4 is stopped as shown in FIG. 3 (a).

Further, when the input voltage Vac is positive and the voltage further increases to be larger than the forward voltage 3/4 * n * V _{F for the} n LED modules 110, the input current is rectified passes through a diode (BD ₁₎ of 10), a current starts to flow through the MOSFET Q ₂ is already on that pass through the _{3/4 (D 1, D 2,} D 3) of the LED module (110) (D ₁ , D ₂ , D ₃ radiation). The flowing current is converted to a voltage through the sensing resistors R _sen2 + R _sen1 , which drives the gate of q ₂ through R _off2 . Of course, this time the voltage across the gate of q ₂ is R _off2 and R _gs2 is determined by the distribution voltage of the resistance voltage when driving the q _2, a secondary current flowing through the MOSFET Q ₂ i _Q2 is constant as shown in Figure 3 (a) Lt; / RTI > Wherein R _off2 and R _gs2 resistance value of the current i _Q2 is designed to be larger than the current i _Q3 increases, the voltage change via the sensing resistor (R _sen2 + R _sen1) and, when this design the auxiliary current i _Q2 Since with constant control at the same time by turning on the MOSFET q ₃ and q ₄ through R _off3 and R _off4 to the voltage completely (on), to stop the operation of the auxiliary switch q ₃ and q ₄ (0ff), the existing flowing current i _Q3 and i _Q4 stops the current flow as shown in Fig. 3 (a).

When the input voltage Vac is positive and the voltage further increases and becomes greater than the total forward voltage n * VF for the n LED modules 110, the input current flows through the diode BD ₁ of the rectifying section 10, D ₁ , D ₂ , D ₃ , D ₄ ) and starts to flow through the MOSFET Q ₁ that has been already turned on (D ₁ , D ₂ , D ₃ , D 4 ₄ radiation). The flowing current turns into a voltage through the sensing resistor (R _sen1 ), which drives the gate of q ₁ through R _S1 . Of course, this time the voltage across the gate of q ₁ is R _S1 and R _gs1 is determined by the distribution voltage of the resistance voltage when driving the q _1, flowing through the MOSFET Q ₁ the main current i _Q1 is constant as shown in Figure 3 (a) Lt; / RTI > Wherein R _S1 and R _gs1 resistance value of the current i _Q1 is designed to be larger than the current i _Q2 increases, the voltage change through the sense resistor (R _sen1) and, doing so with constant control of the main current i _Q1 design Since at the same time R _off2, R _off3 and R _off4 through MOSFET q _2, by turning on the q ₃ and q ₄ completely (on), the auxiliary switch q _2, stops the operation of q ₃ and q ₄ (0ff) to this voltage, the existing The currents i _Q2 , i _Q3 and i _Q4 that have flowed are stopped as shown in Fig. 3 (a). As shown in the simulation result of FIG. 7, the current levels of the above four stages can be confirmed through simulation.

That is, when the auxiliary switches Q ₂ , Q ₃ , and Q ₄ operate, the MOSFETs q ₂ , q ₃ , and q ₄ operate in an active region to control the current, and the main switch Q ₁ ) Operates, or when another auxiliary switch is operated and current flows, the operation of the auxiliary switch connected to the auxiliary switch is stopped.

4, the LED module 210 includes four LEDs D ₁ , D ₂ , D ₃ , and D ₄ , and the LED module 210 includes four LEDs D _1, , D ₂ , D ₃ ), it can be operated similarly as described above.

That is, a control circuit (not shown) including each three-terminal switch Q ₁ , Q ₂ , Q ₃ connected to each negative terminal of the series-connected LEDs D ₁ , D ₂ , D ₃ of the LED module 210 (I _Q1 , i _Q2 , i _Q3 ) flowing from each negative terminal connection point of the LEDs (D ₁ , D ₂ , D ₃ ) to the ground terminal to control the rise One or more LEDs (D ₁ , D ₂ ) on the positive terminal side and the last LED (D ₃ ) on the negative terminal side constituting the LEDs of the LED module 210 are sequentially emitted in the descending order and sequentially turned off in the reverse order Can operate. Again, both are made of the same circuit without diode as in the conventional circuit for controlling the switch (Q _3, Q ₂₎ for each of the secondary current (switch Q _3, a circuit coupled to the gate terminal of Q _2, respectively).

For example, the auxiliary current i _Q3 is interrupted when the main current i _Q1 flows or the auxiliary current i _Q2 flows, and when the input voltage Vac is greater than the forward voltage of 1/3 of the LED module 210, i _Q3 flows and the auxiliary voltage i _Q2 flows when the input voltage Vac is larger than the forward voltage of 2/3 of the LED module 210 and the input voltage Vac reaches 3/3 of the forward voltage of the LED module 210 , The main current i _Q1 flows. This can be easily understood with reference to FIG. 5 showing the relationship between the main current and the auxiliary currents (i _Q1 , i _Q2 , i _Q3 ) according to the change of the input power source (V _ac ).

FIG. 6 shows an embodiment in which a dimming circuit is added to the circuit of FIG. 2. FIG.

6, an LED driving circuit according to another embodiment of the present invention drives an LED module 110 having two or more LEDs (e.g., D ₁ , D ₂ , D ₃ , and D ₄ ) A rectifying section 10, a dimming circuit 120, and other control circuits. The dimming circuit 120 includes photocouplers PC0, PC1 and PC2, a capacitor C _on , a zener diode ZD _on , three-terminal switches Q _on , q ₅ and q ₆ , resistors R _dim0 , R _dim1 , R _dim2 , R _sen12 , R _sen13 , R _B5 , R _B6 ), and switches SW0, SW1, and SW2.

Here, the dimming can be controlled according to the signals of the external switches SW0, SW1, and SW2, that is, the on / off of Q _on or the sensing resistances R _sen12 and R _sen13 to the sensing resistance R _sen1 Dimming is controlled so that the brightness of each stage can be adjusted. 6, N terminals (N is a natural number) are connected to a circuit 20 including a resistor R _sen1 connected to the other terminal of the main current switch Q ₁ to which a corresponding LED (for example, D ₄ ) A dimming circuit 120 including a photocoupler (three PC0, PC1 and PC2 in the example of the figure) is connected and the respective switches SW0, SW1 and SW2 connected to the photocouplers are turned on or off, It is possible to perform a plurality of dimming steps (for example, 2 ^N-1 + 1) according to the ON or OFF combination of the switches SW0, SW1, and SW2 by changing the resistance value connected to the R _sen1 .

For example, switch SW0 is when one photocoupler PC0 1 side (diode), a current flows in the secondary side transistor curl collected in-emitter agent is is a lower voltage saturation switch Q _on is turned off, whereby the LED module ( The diodes D ₁ , D ₂ , D ₃ , and D ₄ of the transistors 110 and 110 are turned off so that the lowest I-level (0%) dimming can be performed.

Also, in the switch SW0 OFF state, the switches SW1 and SW2 is when on, MOSFET q _5, q ₆ are both off-sensing resistor may be formed of the second phase II dimming to R _sen2 + R _sen1 (Fig. 8 ( b) the input current waveform to the LED module).

Also, in the switch SW0 is turned off, the switch SW1 is turned on when the switch SW2 is turned off is off-q _5, q ₆ are on, whereby the sensing resistance R + _sen2 Rsen1 // R _sen13 to be the dimming of a third phase III (R _sen13 > R _{sen12 is} assumed). Quot; // "means a parallel resistance value (see the input current waveform to the LED module of FIG. 8 (c)).

In addition, by being in the off state, the switch SW0, a switch SW1 is off and the switch SW2 is turned on is onmyeon q _5, q ₆ are turned off, the sensing resistor R _sen2 + R // R _{sen1 sen12} may be made to the IV phase of the fourth dimming (R _sen13> R assuming _sen12) (see the waveform of the input current to the LED module of Fig. 8 (b)).

Also, in the switch SW0 is turned off, the switches SW1 and SW2 are turned off when, MOSFET q _5, q ₆ both being on the sensing resistance R _{sen2 sen1} + R // R R // _{sen12 sen13} fifth highest in the V-step (100%) dimming can be performed (see the input current waveform to the LED module in FIG. 8 (a)).

Up to now, a driving method when the LEDs (D ₁ , D ₂ , D ₃ , D ₄ ) of the LED module 110 are made of DC (Direct Current) LED elements has been described. However, those skilled in the art can similarly apply it to drive an AC (Alternating Current) LED module through a slight design change to the control circuit for the LED module made of the DC LED elements described above. For example, the above-described operation method of the control circuit can be applied to drive the LED module made up of the AC LED elements without the rectifying part 10, and can be easily used.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

110, 210: LED module
120: a dimming circuit

Claims (6)

And a control circuit for controlling each current flowing from the respective terminal connection point to the ground terminal by using respective three-terminal switches connected to respective negative terminals of a plurality of LEDs (Light Emitting Diodes) connected in series, ,
In order to sequentially turn on one or more LEDs on the positive terminal side of the plurality of LEDs and the last LED on the negative terminal side in order of the rising and falling of the power supplied to the plurality of LEDs,
Wherein the control circuit includes a switch for an auxiliary current connected to the one or more LEDs sequentially turned on in accordance with the rise of the power source and a switch for main current connected to the last LED, The main current switch and the auxiliary current switch are sequentially turned off to turn off the corresponding LED,
The other terminal of the auxiliary current switch and the terminal of the circuit for turning off the auxiliary current switch are both connected to the same contact and the same contact is connected to a resistor through which the current flows when the main current switch is turned on ,
A metal-oxide-semiconductor field-effect transistor (MOSFET), a bipolar transistor, or a shunt regulator is used as a three-terminal switch for controlling or turning off the current of the main current switch,
Wherein a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar transistor is used as a three-terminal switch for controlling or turning off the current of the at least one auxiliary current switch. The method according to claim 1,
Wherein a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or a bipolar transistor is used as the main current switch and the at least one auxiliary current three-terminal switch. delete delete The method according to claim 1,
A circuit including N (N is a natural number) photocouplers is connected to a circuit including a resistor whose one terminal is connected to another terminal of the main current switch to which the corresponding LED is connected, and each switch connected to the photocoupler is turned on And a plurality of dimming steps corresponding to ON or OFF combinations of the switches are performed by changing a resistance connected to a resistor connected to the other terminal. The method according to claim 1,
An LED module having the plurality of LEDs formed of DC LED elements, or an LED module having the plurality of LEDs formed of AC LED elements.

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