WO2010134721A9 - Multilayer led power factor correction circuit - Google Patents

Abstract

The present invention relates to a multilayer power factor correction (PFC) circuit in which two or more PFC circuits for correcting a power factor during the operation of light-emitting diodes (LEDs) are constituted by condensers, diodes, etc., and arranged in parallel to each other, and conductive noise between individual PFCs are cutoff through a noise filter to ensure a high power factor even at a low capacity power level. The multilayer LED power factor correction circuit according to the present invention comprises: a power unit for supplying alternating current (AC) power; a filter unit for filtering noise of an input terminal to which the AC power is applied, and noise of an interior of the circuit; a rectifying unit for converting the input of the AC power into pulsating direct current (DC) power; a multilayer correcting unit for smoothing the pulsating DC power by two or more PFC circuits and reducing conductive noises; and an LED-driving unit for converting the smoothed pulsating DC power into low voltage in accordance with a switching operation, and transmitting the low voltage to an LED array to enable the LED array to emit light. The present invention maintains the power factor of a circuit of an LED lamp which operates at a low capacity of 5 watt (W) power, at the level of 90%. In addition, an LED lamp circuit, which maintains a power factor of 92% at 5 to 8 watt (W) power, can be produced. Further, an LED lamp circuit, in which conductive EMC noise satisfy the reference value even at a low capacity of power, can be produced.

Description

Multi-layer LED Power Factor Correction Circuit

The present invention relates to a power factor correction circuit, and more particularly, to a PFC circuit that compensates for power factor when a light emitting diode (LED) is driven, in which two or more PFC circuits including a capacitor and a diode are configured in parallel. And a noise filter between the PFCs to block conductive noise between individual PFCs, thereby ensuring a high power factor even at a low power level.

In general, LED lighting products connected directly to an AC power source must have a circuit built in a limited space. Therefore, a method using a step-down buck converter type IC capable of high voltage connection is possible. Most common. This method is actually widely used all over the world, and is configured as shown in FIG.

1 is a circuit diagram showing a conventional AC power LED lighting circuit.

Referring to FIG. 1, the conventional AC power type LED lighting circuit 100 includes a noise filter 110, a rectifier circuit 120, a smoothing circuit 130, and an LED / converter circuit 140. .

The conventional AC power LED lighting circuit 100 configured as described above blocks the noise at the input terminal and the inside by the noise filter 110, and converts the AC input into the pulsating DC current by the rectifier circuit 120. Then, the pulsating DC current is smoothed to the current used in the LED / converter circuit 140 by the smoothing circuit 130 and supplied to the LEDs arranged in series or in parallel by the LED / converter circuit 140 so that the LED bulb is Light emission.

However, two main problems occurring in the conventional AC power type LED lighting circuit 100 are as follows.

1) A large capacity capacitor is usually used in the rectifier circuit 120. In this process, a power factor decrease due to a phase difference between voltage and current occurs. In general, the power factor is 50 to 60% when the capacitor is smoothed. Since the power factor is low, spike current often occurs, and a lot of harmonic components are generated, which lowers the stability of the product, and the application of the power factor is very limited.

2) In the process of converting the high voltage to the low voltage capable of driving the LED, a considerable level of conductive noise is generated by the high-speed switching action of the FET controlling the high voltage.

The method commonly used as a solution to this problem is as follows.

First, the power factor drop problem is composed of a power factor correction circuit (hereinafter referred to as PFC) by combining two capacitors in series with the smoothing circuit 130 and combining diodes as shown in FIG. It can be improved.

Second, the conductive noise (NOISE) problem blocks the noise by configuring a filter circuit combining a line filter and a capacitor at the output terminal as shown in (c) of FIG.

The above-described method is a widely used method in general companies, and this method also has the following problems and limitations.

1) Even if the power factor correction circuit (PFC) is configured, power factor of 90% is realized only at power capacity of 8W or more, and power factor of 85W or less falls to 85% or less. have.

2) When the power factor correction circuit (PFC) is configured, the internal noise is more affected than when the basic smoothing circuit is configured, and there is a problem in that conductive EMC noise is additionally generated.

3) In order to further block the conductive EMC noise, the component of the filter circuit at the output stage must be strengthened. In this case, the reactance component of the coil-X capacitor of the filter is increased to further decrease the power factor. The standard has a problem of falling to the level of 70% of power factor and 50% at the level of 5 watts (W).

In other words, the power factor and the conductive EMC noise have the characteristics of deteriorating the opposite side when one side is improved, so it is virtually impossible to solve both of them.

In addition, this problem can be partially solved by using an IC-type power factor correction circuit, ACTIVE PFC, which is used in commercially available switching mode power supplies (SMPS). There is a problem that the power factor is increased significantly, especially the volume is increased, which is also guaranteed only a large capacity of more than 10 watts (W).

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide two or more PFCs composed of two capacitors and a circuit such as a diode in parallel to a PFC circuit that compensates for power factor when driving a light emitting diode (LED). By providing a double layer and connecting noise filters between the PFCs to conduct conductive noise blocking between individual PFCs, a multi-layered LED power factor correction circuit can be ensured even at a low power level.

Multi-layer LED power factor correction circuit according to the present invention for solving the above problems, the power supply unit for supplying AC (AC) power; A filtering unit filtering the input terminal to which the AC power is applied and noise inside; A rectifier for converting an input of the AC power source into a pulsating DC power source; A multilayer compensation unit for smoothing the pulsating direct current (DC) power supply by two or more power factor correction circuits (PFCs) and attenuating conductive noises; And an LED driver for converting the smoothed pulsating direct current (DC) power into a low voltage according to a switching operation and transferring the smoothed pulsating direct current (DC) power to the LED array to emit the LED array.

Here, the multilayer compensation unit, each power factor correction circuit includes a plurality of capacitors and two or more diodes, a noise filter for attenuating the conductive noise between the power factor correction circuit is connected.

In the power factor correction circuit, a first capacitor C1, a first diode D1, and a second capacitor C2 are connected in series, and the first capacitor C1 and the first diode D1 are connected in series. The second diode D2 is connected in parallel to the direction of the first diode D1 so as to include the connection of the first diode D1, and the first diode D1 and the second capacitor C2 include the connection of the first diode D1 and the second capacitor C2. In contrast to the direction of the first diode D1, the third diode D3 is connected in parallel.

In addition, the two or more power factor correction circuits are connected in parallel, a noise filter is connected between the power factor correction circuits to which the pulsating direct current (DC) power is applied, and the power factor correction circuits to which the pulsating direct current (DC) power is output differs. The noise filter is connected.

The LED driving unit may include: a switching element configured to perform a switching operation so that the pulsating direct current (DC) power is applied or cut off to the LED array; A control IC controlling the switching operation; An inductor for storing power by on / off operation of the control IC and supplying the power to the LED array; It includes a current sensing resistor for controlling the current flowing in the LED array.

The current sensing resistor is connected between the control IC and the switch element, and the control IC is used to measure the voltage of the current sensing terminal of the control IC to control the current on the LED array side.

According to the present invention, the power factor of an LED lighting circuit operating at a low power capacity of 5 watts (W) can be maintained at a level of 90%.

In addition, it is possible to implement an LED lighting circuit that maintains a power factor of 92% at a power capacity of 7 to 8 watts (W).

In addition, the conventional circuit requires a power factor correction circuit and an input noise filter, so that the circuit volume must be greatly increased. However, in the present invention, the volume of the input noise filter can be greatly reduced, and a small filter component can be configured between the multilayer PFCs. A miniaturized circuit can be implemented.

In addition, it is possible to realize an LED lighting circuit whose conductive EMC noise satisfies the reference value even at a low power capacity.

1 is a circuit diagram showing a conventional AC power LED lighting circuit.

2 is a diagram illustrating a multilayer LED power factor correction circuit according to an exemplary embodiment of the present invention.

3 to 5 are diagrams showing a power factor graph by a general LED lighting circuit.

6 and 7 are diagrams showing a power factor graph by the multilayer LED power factor correction circuit according to the present invention.

<Description of Symbols for Main Parts of Drawings>

100: conventional AC power LED lighting circuit 110: noise filter

120: rectifier circuit 130: smoothing circuit

140: LED / converter circuit 200: multilayer LED power factor correction circuit

210: power supply unit 220: filtration unit

230: rectifying unit 240: multilayer compensation unit

242, 244: PFC 246, 248: noise filter

250: driver 251: control IC

252: LED array 253: Inductor

254: flywheel diode 255: switching element

256: current sense resistor

Details of the object and technical configuration of the present invention and the resulting effects thereof will be more clearly understood by the following detailed description based on the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating a multilayer LED power factor correction circuit according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the multilayer LED power factor correction circuit 200 according to the present invention includes a power supply unit 210, a noise filtering unit 220, a rectifier unit 230, and a multilayer compensation unit 240. ) And an LED driver 250.

The power supply unit 210 supplies AC power.

The filter unit 220 filters an input terminal to which an AC power is applied and noise inside. At this time, the filtration unit 220 is usually composed of X-capacitor, choke coil and the like. Lighting products used in the form of socket-mounts generally do not have a ground terminal, so no Y capacitor is used to connect to ground.

The rectifier 230 is a circuit for converting an input of an AC power source into a pulsating direct current (DC) power source, and a bridge circuit in which diodes are arranged symmetrically is widely used.

The multilayer compensation unit 240 is a circuit for smoothing the pulsating direct current (DC) power supply by two or more power factor correction circuits (PFCs) and attenuating conductive noise. In this case, the multilayer compensation unit 240 is a smoothing function, and since the pulsating direct current changes from 0 to 1.4 times the voltage of the AC voltage at regular intervals, it is a circuit for smoothing it for use in an LED circuit driven by DC. Use a smoothing condenser.

In addition, the multilayer compensator 240 includes a noise filter for each power factor correction circuit 242 and 244 including a plurality of capacitors and two or more diodes to attenuate conductive noise between the power factor correction circuits 242 and 244. 246, 248 are connected.

In addition, each of the power factor correction circuits 242 and 244 is connected to the first capacitor C1, the first diode D1, and the second capacitor C2 in series, and the first capacitor C1 and the first diode ( The second diode D2 is connected in parallel in a direction opposite to the direction of the first diode D1 to include the connection of D1), and includes a connection of the first diode D1 and the second capacitor C2. The third diode D3 is connected in parallel in a direction opposite to that of the first diode D1.

In addition, the multilayer compensation unit 240 includes two or more power factor correction circuits 242 and 244 connected in parallel, and a noise filter 246 between the power factor correction circuits 242 and 244 to which pulsating direct current (DC) power is applied. Another noise filter 248 is connected between the power factor correction circuits 242 and 244 to which the pulsating direct current (DC) power is output.

That is, the noise generated by the LED driver 250 is first blocked by the noise filter, thereby reducing the amount of conductive noise going to the input terminal, thereby greatly reducing the burden on the filter unit 220, and reducing the noise filter connected between individual PFCs. 246 and 248 have a low imaginary component of reactance and have little effect on the power factor.

The LED driver 250 converts the smoothed pulsating direct current (DC) power into a low voltage according to a switching operation and transmits the converted voltage to the LED array 252 to emit the LED array.

The LED driver 250 may include a control IC 251, an LED array 252, an inductor 253, a flywheel diode 254, and a switching FET. 255 and Current Sensing Resister 256.

The LED array 252 places the LEDs in series or in parallel in appropriate quantities depending on the capacity of the lighting product.

The switching element 255 performs a switching operation such that a pulsating direct current (DC) power is applied or cut off to the LED array 252.

The switching element 255 may be implemented by, for example, a field effect transistor (FET), and is responsible for a power switching operation of turning on / off power by receiving a switching signal of the control IC 251, and some products may control the control IC 251. You can also implement types that are integrated with.

The control IC 251 controls the switching operation of the switching element 255. The control IC 251 uses the pulsating DC output of the multilayer compensation unit 240 as an input, and has a low voltage to be applied to the LED array 252 through the switching operation. An IC that controls the switching operation to be converted.

The inductor 253 stores power by the on / off operation of the control IC 251 and supplies the power to the LED array 252.

The flywheel diode 254 functions to cancel the reflux current of the inductor 253.

The current sense resistor 256 is used to measure the current flowing in the LED array 252. At this time, the current sense resistor 256 is connected between the control IC 251 and the switching element 255, the control IC 251 measures the voltage of the current sensing terminal of the control IC to the current of the LED array 252 side It is used to control. That is, the current sense resistor 256 is normally connected to the source terminal of the FET and the current sensing terminal of the control IC 251. In general, the current of the LED is controlled by measuring the voltage of the terminal.

In the multilayer LED power factor correction circuit 200 according to the present invention configured as described above, the AC power is applied from the power supply unit 210 to the rectifying unit 230 while the noise is filtered through the filtering unit 220, and the rectifying unit 230. Is converted to the pulsating direct current of the DC power supply.

Subsequently, the pulsating direct current is smoothed through the multilayer compensation unit 240, and the conductive EMC noise is blocked by the noise filters 246 and 248 to be transmitted to the LED driver 250.

Therefore, the LED driver 250 applies a pulsating direct current applied from the multilayer compensation unit 240 to the LED array 252 to emit a plurality of LEDs. At this time, the control IC 251 controls the switching operation of the switching element 255 to adjust a plurality of LED light emitting state, by measuring the current on the LED side through the current sense resistor 256.

3 to 5 are diagrams illustrating a power factor graph by a general LED lighting circuit.

In the case of FIG. 3, the power factor is about 70% when only the noise filter is applied to the general LED lighting circuit without applying the power factor correction circuit (PFC).

In the case of FIG. 4, when the power factor correction circuit (PFC) is applied to the existing LED lighting circuit and the noise filter is not applied, the power factor is about 94% when the power is 7 Watt (W).

In the case of FIG. 5, a power factor correction circuit (PFC) is applied to a conventional LED lighting circuit and a noise filter is also applied, and the power factor is about 70% when the power of the power is 7 Watt (W).

In contrast, FIGS. 6 and 7 are graphs illustrating power factor graphs of the multilayer LED power factor correction circuit according to the present invention.

In the case of FIG. 6, in the multi-layered LED power factor correction circuit 200 according to the present invention, the power factor correction circuit PFC is applied in two layers, and a noise filter is applied between the power factor correction circuits PFC. It can be seen that the power factor is 92% at the (W) level. Therefore, it can be seen that the multilayer LED power factor correction circuit 200 according to the present invention has improved 22% compared to the 70% power factor of the existing 7 Watt (W) class LED lighting circuit.

Multi-layer LED power factor correction circuit 200 according to the present invention comprises a power factor correction circuit (PFC) in two stages, by connecting a noise filter between the two power factor correction circuit (PFC), the power source power is 7 Watt (W) class In the case of applying, the result was that the EMC power factor satisfies the reference value when the power factor is about 0.92.

In the case of FIG. 7, in the multi-layer LED power factor correction circuit 200 according to the present invention, the power factor correction circuit PFC is applied to two multilayers, and a noise filter is applied between the power factor correction circuits PFC. It can be seen that the power factor is about 91% at the (W) level. Therefore, it can be seen that the multilayer LED power factor correction circuit 200 according to the present invention has a 41% improvement over the 50% power factor in the case of the existing 5 Watt (W) class LED lighting circuit.

In addition, the multilayer LED power factor correction circuit 200 according to the present invention comprises a power factor correction circuit (PFC) in two stages, and connects a noise filter between two power factor correction circuits (PFC), so that the power supply is 5 Watts (W). Even at low power capacity, the power factor was maintained at 0.9 level and EMC conducted noise was also satisfied.

As described above, according to the present invention, a PFC circuit that compensates for power factor when driving a light emitting diode (LED) includes two or more PFCs composed of two capacitors and a circuit such as a diode in parallel, By connecting a noise filter between the PFCs to conduct conductive noise blocking between individual PFCs, a multi-layered LED power factor correction circuit can be realized to ensure high power factor even at a low power level.

As those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features, the embodiments described above should be understood as illustrative and not restrictive in all respects. Should be. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

The present invention is applicable to LED lighting products using AC power.

It can also be applied to LED lighting products with tight power factor and EMC regulations, and to LED lighting circuits with very low power capacity.

It can also be applied to AC power input application products using BUCK CONVERTER IC.

In addition, conductive power may be blocked and a high power factor may be applied to a power supply that converts an AC voltage into a DC for driving a LED.

Claims (6)

A power supply unit supplying AC power; A filtering unit filtering the input terminal to which the AC power is applied and noise inside; A rectifier for converting an input of the AC power source into a pulsating DC power source; A multilayer compensation unit for smoothing the pulsating direct current (DC) power supply by two or more power factor correction circuits (PFCs) and attenuating conductive noises; And An LED driver converting the smoothed pulsating direct current (DC) power into a low voltage according to a switching operation and transferring the smoothed pulsating direct current (DC) power to an LED array to emit an LED array; Multi-layer LED power factor correction circuit comprising a. The method of claim 1, The multilayer compensation power factor correction circuit, wherein each power factor correction circuit includes a plurality of capacitors and two or more diodes, and a noise filter for attenuating the conductive noise between the power factor correction circuits is connected. The method of claim 2, In each of the power factor correction circuits, a first capacitor C1, a first diode D1, and a second capacitor C2 are connected in series, and the first capacitor C1 is connected to the first diode D1. In contrast to the direction of the first diode (D1) to include a second diode (D2) is connected in parallel, the first diode to include a connection of the first diode (D1) and the second capacitor (C2). The multilayer LED power factor correction circuit, wherein the third diode D3 is connected in parallel to the direction of the direction D1. The method of claim 1, The noise filter is connected between the two or more power factor correction circuits in parallel, the power factor correction circuit to which the pulsating direct current (DC) power is applied, and the noise filter is different between the power factor correction circuit to which the pulsating direct current (DC) power is output. The multi-layer LED power factor correction circuit characterized in that is connected. The method of claim 1, The LED driver may include: a switching element configured to perform a switching operation such that the pulsating direct current (DC) power is applied or cut off to the LED array; A control IC controlling the switching operation; An inductor for storing power by on / off operation of the control IC and supplying the power to the LED array; And a current sensing resistor for controlling a current flowing in the LED array. The method of claim 5, The current sensing resistor is connected between the control IC and the switch element, the control IC is used to measure the voltage of the current sensing terminal of the control IC to control the current on the LED array side LED power factor correction circuit.

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