WO2011159002A1 - Sine wave constant current led driving circuit and a method thereof - Google Patents

Abstract

An LED driving circuit for driving an LED module that has a plurality of LEDs connected serially along one surface of the present invention comprises: a bridge diode for rectifying an incoming alternating current to a direct current and then providing the rectified power to the LED module; and a control circuit connected to respective contact points with the plurality of serially connected LEDs, for controlling a current flowing from each contact point to a ground terminal.

Description

Sinusoidal constant current LED drive circuit and method

The present invention relates to a LED driving circuit and method, in order to directly drive a light emitting diode (LED) to an alternating current (AC) power source, driving an input AC current with a sinusoidal current suitable for harmonic regulation and power factor regulation, The present invention relates to a LED driving circuit and a method capable of driving at a constant current so that the current is kept constant even when the input AC voltage is fluctuated so that the flicker characteristic is excellent.

1 is a view for explaining a conventional LED driving circuit. As shown in FIG. 1, the conventional LED driving circuit applies an AC power supply voltage Vac to two input terminals of the bridge diodes D1 to D4, and sends a current rectified by the bridge diodes D1 to D4 to the resistor R. According to the current controlled by the resistor R, the LEDs D _{1 , 1} to D _{n , n} provided to be connected in parallel to the LED module are driven to emit light.

As described above, the conventional LED driving circuit by controlling the current of the resistor R has a very easy and simple structure. However, in order to supply a constant current to the LED module, the AC power supply voltage Vac must always be supplied at a constant voltage. The AC supply voltage Vac is a voltage of 10-20% of the voltage of a commercial system, and the voltage fluctuation rate may be even higher in a dense or commercial area where a large capacity induction device is used. In addition, voltages in commercial systems have a frequency variation of less than 5%.

Therefore, the conventional LED driving circuit using only the resistance R as described above is very limited in constant current driving to secure the lifetime and light characteristics of the LED, and thus may cause flicker (light flicker) and the like. Failure to maintain a constant Vf (operating voltage) of the changing LED can be a factor to shorten the life of the LED.

Accordingly, an object of the present invention is to solve the above-described problems, and an object of the present invention is to drive an input AC current with a sinusoidal current suitable for harmonic regulation and power factor regulation in driving an LED directly with an AC power supply, and input AC The present invention provides a LED driving circuit and a method capable of driving a constant current to maintain excellent flicker characteristics even with a change in voltage.

For this purpose, the LEDs of the parallel connection provided in the LED module are controlled so that each connection point connected in series is driven independently, so that the current coming from each connection point is basically a constant current, wherein the LEDs of each parallel connection have a specific forward direction. The present invention provides a LED driving circuit and method capable of emitting light by allowing a constant current to flow for a short time when a voltage is formed, or emitting light by continuously flowing a constant current, or emitting both in parallel.

First, to summarize the features of the present invention, the LED drive circuit for driving an LED module having a plurality of LEDs connected in series in accordance with an aspect of the present invention for achieving the above object of the present invention, the AC power is received by direct current Rectifier for rectifying and supplying the rectified power to the LED module; And a control circuit connected to each connection point of the series-connected LEDs to control respective currents flowing from each connection point to the ground terminal.

Each of the plurality of LEDs connected in series in the LED module includes a plurality of LEDs connected in parallel.

The rectifying portion is made of a bridge diode.

The control circuit is configured to sequentially emit light of the series-connected LEDs as power supplied to the LED module increases, and to include next-emitted LEDs so that the next LEDs may emit light together. Control the current to have the same amount of current.

Alternatively, the control circuit may sequentially emit the plurality of LEDs connected in series as power supplied to the LED module increases, but currents flowing from the connection point to the ground terminal are turned off so that the previous LEDs are turned off and the next LED emits light. Control to have increased current as a constant increase function.

Alternatively, the control circuit may sequentially emit the plurality of LEDs connected in series as the power supplied to the LED module increases, but may flow from the respective connection points to the ground terminal so that the next LED may emit the same together, including the previously emitted LEDs. A first way of controlling each current to have the same magnitude of current is applied to some of the plurality of LEDs, the currents flowing from the junction to the ground terminal so that the previous LEDs are off and the next LED emits a constant increase function. The second method of controlling to have an increased current is applied to the rest of the plurality of LEDs other than the part to which the first method is applied.

The control circuit turns on or off a control rectifying element at each connection point according to the magnitude of the current flowing through the switch to the ground terminal, so that the switch connects or opens between each connection point and ground.

The LED driving method for driving an LED module having a plurality of LEDs connected in series according to another aspect of the present invention includes receiving an AC power using a bridge diode to rectify the DC and supplying the rectified power to the LED module. step; And controlling each current flowing from each connection point of the series-connected LEDs to the ground terminal.

According to the LED driving circuit and method according to the present invention, by controlling each connection point connected in series with the LEDs of the parallel connection provided in the LED module to be driven independently, so that the current coming from each connection point is basically a constant current, at this time The LEDs in each parallel connection can cause a constant current to flow for only a short time when a specific forward voltage is formed, or to continuously flow a constant current, or drive the LED modules in parallel.

Accordingly, the input AC current can be driven with a sinusoidal current suitable for harmonic regulation and power factor regulation, and the LED module can be driven so that the constant current is maintained even when the input AC voltage is fluctuated so as to have excellent flicker characteristics.

In addition, in the case of constructing a power supply using energy storage devices such as L (inductor or transformer) and C (capacitor), there is a limit to integration into semiconductors, but the LED driving circuit according to the present invention is a transistor without an energy storage device. And, since it consists of a circuit that can be implemented in a semiconductor such as a resistor can be easily integrated into a semiconductor circuit.

1 is a view for explaining a conventional LED driving circuit.

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

3 is a block diagram of a control circuit according to an embodiment of the present invention.

4 is a view for explaining a horizontal sum current driving method according to an embodiment of the present invention.

5 is a view for explaining a vertical sum current driving method according to an embodiment of the present invention.

6 is a view for explaining a combined current driving method according to an embodiment of the present invention.

7 is a view for explaining the generation of sinusoidal current of the current driving schemes according to the present invention.

8 is a view for explaining a measurement waveform of the LED driving circuit according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments.

2 is a view for explaining the LED driving circuit 10 according to an embodiment of the present invention.

2, the LED driving circuit 10 according to the exemplary embodiment of the present invention includes a bridge diode 11 and a control circuit 12 to drive the LED module 13.

The bridge diode 11 is a rectifying circuit that receives the AC power Vac and rectifies the DC. The bridge diode 11 supplies the rectified power to the LED module 13 through two output terminals. In the bridge diode 11, two sets of two diodes D1, D2 / D3, and D4 connected in series are connected in parallel, the series connection points are input terminals of the AC power supply Vac, and the parallel connection points are output terminals. .

The LEDs of the LED module 13 may emit light according to the rectified power source from the bridge diode 11. The LED module 13 includes a plurality of LEDs connected in series (eg, D _{1 , 1} , D _{1 , 2} , .., D _{1, n-1} , D _{1 , n} ), as shown in FIG. 2, in parallel Multiple LEDs connected (for example, D _{1 , 1} , .. D _{n , 1} in parallel, D _{1 , 2} , .. D _{n , 2} in parallel, .., D _{1 , n-1} , .. D _{n ,} a plurality of sets of parallel, D _{1, n,} D _{n .., n} of the parallel _{n- 1)} may be a structure in series.

In particular, in the present invention, the control circuit 12 is connected to each connection point of a plurality of LEDs connected in series of the LED module 13, and controls each current flowing from each connection point to the ground terminal. For example, the control circuit 12 controls each connection point of the plurality of LEDs connected in series of the LED module 13 to be driven independently, so that the current coming from each connection point is basically a constant current, and at this time, the plurality of LEDs connected in series Each (may be each set of parallel-connected LEDs) allows a constant current to flow for only a short time when a specific forward voltage is formed, or to continuously flow a constant current, or both in parallel You can also drive.

3 is a block diagram of a control circuit 12 according to an embodiment of the present invention.

Referring to FIG. 3, the control circuit 12 according to an exemplary embodiment of the present invention may include connection points YN ₁ , YN ₂ , .. YN _{n −1} , YN of a plurality of LEDs connected in series of the LED module 13. _n ) connected to a switch (e.g. Q1), a control rectifying element (e.g. SCR: Silicon Controlled Rectifier) (e.g. REG1), resistors (e.g. R ₁ , R _{sen _1} ) It may include a bias circuit for supplying a constant DC bias voltage (V _B ) to each connection point. The switch referred to herein may be a metal oxide semiconductor field effect transistor (MOSFET), in particular, may be an N-type MOSFET as shown in FIG. 3, and in some cases, may be replaced by a P-type MOSFET with some circuit changes.

The bias circuit includes a resistor (R _B ) and a zener diode (ZD ₁ ) connected in series between a constant power supply (CN) and ground, and the gate and drain terminals of the switch (Q _B ) are connected across the resistor (R _B ). And a bias voltage V _B may be output through a source, which is the remaining terminal of the switch Q _B.

Accordingly, at each connection point (YN ₁ , YN ₂ , .., YN _{n -1} , YN _n ), the control rectifying element (eg, depending on the magnitude of the current flowing through the switch (eg Q1) to the ground terminal) , REG1) on or off, so that a switch (e.g., Q1) connects each connection point (YN ₁ , YN ₂ , .., YN _n-1 , YN _n ) to ground. Or open it.

According to the operation of the control circuit 12, the current from each connection point (YN ₁ , YN ₂ , ..., YN _{n -1} , YN _n ) is controlled to be a constant current, and at this time, each of the plurality of LEDs connected in series When this specific forward voltage is formed, the constant current may flow for only a short time, the constant current may flow continuously, or both may drive the LED module 13 in parallel.

The operation of the control circuit 12 will be described in more detail with reference to FIGS. 4 to 8.

4 is a view for explaining a horizontal sum current driving method according to an embodiment of the present invention.

As shown in FIG. 4, the control circuit 12 includes the respective currents i _D1 , which flow from the respective connection points YN ₁ , YN ₂ ,..., YN _{n −1} , YN _n to the ground terminal in the horizontal sum current driving scheme. i _D2 , .., i _{Dn -1} , i _Dn ) can be controlled to have the same current. For example, as the power supplied from the bridge diode 11 to the LED module 13 increases (e.g., sinusoidal wave), the plurality of series-connected LEDs of the LED module 13 are sequentially lighted, but the previously emitted LEDs are lighted. Including the next LED to emit light together, each of the current flowing out of the lighted LED through the control circuit 12 to the ground terminal can be controlled to have the same current.

The operation of the control circuit 12 is the size of the switch connected to each connection point (YN ₁ , YN ₂ , .., YN _n-1 , YN _n ), the active voltage of the control rectifying element, This can be done by making the sizes of the resistors the same.

At this time, when the horizontal summing the current of the LED light emission, as shown in Figure 7, the power is increased becomes the integrated value of the accumulated electric current it creates a stunning current to a sine wave becomes larger as the respective connecting point ₍₁ YN, YN _2, .. Since each current flowing out from YN _{n -1} and YN _n to the ground terminal through the control circuit 12 is controlled by a constant current of the same magnitude, flicker generation can be suppressed even when the voltage Vac is changed. As shown in FIG. 8, it was confirmed that the sine wave constant current appeared.

5 is a view for explaining a vertical sum current driving method according to an embodiment of the present invention.

As shown in FIG. 5, the control circuit 12 has a constant increasing function (eg, a current) flowing to the ground terminal at each connection point YN ₁ , YN ₂ , .., YN _{n -1} , YN _n in the vertical sum current driving scheme. For example, it can be controlled to have an increased current by the sinusoidal function). For example, the magnitude of each of the currents i _D1 , i _D2 , .., i _{Dn −1} , i _Dn is different, and as the power supplied from the bridge diode 11 to the LED module 13 increases ( For example, the sine wave LED module 13 sequentially emits a plurality of LEDs connected in series, but turns off the previously emitted LEDs and causes the next LED to emit, while exiting the emitted LEDs and through the control circuit 12 to the ground terminal. The flowing currents can be controlled to have an increased current with a constant increase function (eg, sinusoidal function).

The operation of the control circuit 12 is the size of the switch connected to each connection point (YN ₁ , YN ₂ , .., YN _n-1 , YN _n ), the active voltage of the control rectifying element, This can be done by setting the sizes of the resistors accordingly.

At this time, when vertically summing the current of the light-emitting LED, as shown in Figure 7, as the power is increased the current of each connection point increases to make a current close to the sine wave, each connection point (YN ₁ , YN ₂ , .., Each current flowing out from YN _{n -1} and YN _n to the ground terminal through the control circuit 12 is controlled by a constant current, so that flicker generation can be suppressed even when the voltage Vac is changed. As shown in FIG. 8, it was confirmed that the sine wave constant current appeared.

6 is a view for explaining a combined current driving method according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a combination of a horizontal sum current driving method as shown in FIG. 4 and a vertical sum current driving method as shown in FIG. 5.

As shown in FIG. 6, the control circuit 12 may apply the horizontal sum current driving method as shown in FIG. 4 to some of the plurality of LEDs connected in series in the combination current driving method, and the LED module ( The vertical sum type current driving method as shown in FIG. 5 may be applied to the remaining of the plurality of LEDs connected in series in FIG. 13.

The combination in the same current driving method, when summing the current of the LED light emission, as shown in FIG 7, the approximate current to the sine wave is created as the power increases, the respective connection points ₍₁ YN, YN _2, .., _n YN _Since each current flowing out of _-1 , YN _n to the ground terminal through the control circuit 12 is controlled by a constant current, flicker generation can be suppressed even when the voltage Vac changes. As shown in FIG. 8, it was confirmed that the sine wave constant current appeared.

The operation of such a control circuit 12 is performed in each of the connection points YN ₁ , YN ₂ , .. YN _{n -1} , YN _n for some of the plurality of LEDs connected in series in the LED module 13 in the circuit as shown in FIG. 3. Equal to the size of the switch, the active voltage of the control rectifying element, the size of the resistors, etc., and the respective connection points (YN ₁ , YN ₂ , ..,) for the remaining of the plurality of LEDs connected in series of the LED module 13. YN _n-1 , YN _n ) may be appropriately determined by differently determining the size of the switch connected to the active rectifier element, the size of the active voltage of the control rectifying element, and the size of the resistors.

Since the LED driving circuit 10 according to the present invention described above is composed of a circuit which can be implemented as a semiconductor such as a transistor and a resistor without using an energy reservoir such as L (inductor or transformer) and C (capacitor), It can be easily integrated and implemented.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

Claims (8)

1. An LED driving circuit for driving an LED module having a plurality of LEDs connected in series,

   Rectification unit for receiving the AC power to rectify the DC to supply the rectified power to the LED module; And

   A control circuit connected to each connection point of the series-connected LEDs to control respective currents flowing from each connection point to a ground terminal

   LED driving circuit comprising a.
2. The method of claim 1,

   Each of the plurality of LEDs connected in series in the LED module comprises a plurality of LEDs connected in parallel.
3. The method of claim 1,

   The rectifier is a LED driving circuit, characterized in that consisting of a bridge diode.
4. The method of claim 1,

   The control circuit,

   As the power supplied to the LED module increases, each of the currents flowing from each connection point to the ground terminal has the same magnitude so that the plurality of series-connected LEDs sequentially emit light, and the next LEDs, including the previously emitted LEDs, emit light together. LED driving circuit, characterized in that the control to have a current.
5. The method of claim 1,

   The control circuit,

   As the power supplied to the LED module increases, the current flowing from the connection point to the ground terminal increases as a constant increasing function so that the series-connected LEDs sequentially emit light, but the previous LEDs are turned off and the next LED emits light. LED driving circuit, characterized in that the control to have.
6. The method of claim 1,

   The control circuit,

   As the power supplied to the LED module increases, the plurality of series-connected LEDs sequentially emit light,

   Applying a first scheme to some of the plurality of LEDs such that each current flowing from each connection point to the ground terminal has the same magnitude of current so that the next LED, including previously emitted LEDs, emits together,

   The second method of controlling the currents flowing from the connection point to the ground terminal to have an increased current as a constant increasing function so that the previously emitted LEDs are turned off and the next LED emits other than the part to which the first method of the plurality of LEDs is applied. LED driving circuit, characterized in that applied to the rest of the.
7. The method of claim 1,

   The control circuit,

   And at each connection point, a control rectifying element is turned on or off according to the magnitude of the current flowing through the switch to the ground terminal, so that the switch connects or opens the connection point between each connection point and ground.
8. An LED driving method for driving an LED module having a plurality of LEDs connected in series,

   Receiving an AC power by using a bridge diode to rectify the DC and supplying the rectified power to the LED module; And

   Controlling each current flowing from each connection point of the series-connected LEDs to the ground terminal

   LED driving method comprising a.

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