KR20110037133A - Led driving circuit using sumple current source - Google Patents

Abstract

PURPOSE: An LED driving circuit using a simple current source is provided to implement economical and reliable light source structure by simplifying an LED driving circuit. CONSTITUTION: An LED driver circuit comprises an AC power source(Vin), an inductor(L), a bridge rectifier diode, a switch(S) and an LED. A bridge rectifier diode is comprised of four diodes, wherein a first structure of two diodes are directly connected and a second structure of two diodes are serially connected while two structure are connected in parallel with each other.

Description

LED driving circuit using simple current source {LED Driving Circuit using Sumple Current Source}

The present invention relates to a light emitting diode (LED) driving circuit, which replaces an output capacitor and a rectifying diode with an LED in a basic AC / DC circuit, and provides current control and output power control through energy charging and discharging of an inductor. It is an economical and reliable simple LED driving circuit that enables power factor and simultaneously compensates power factor.

Conventional LED driving circuits use general step-down circuits, step-up circuits, step-up circuits or insulated circuits to control power through current flow through LEDs. As a result, most DC output capacitors exist in the circuit. This method has a disadvantage in that the DC input simply has a large number of circuit components, but in AC input, an additional circuit is necessary for power factor correction. In addition, there are ICs (Integrated Circuits) that drive LEDs using a charge pump method, but they are not suitable for applications with a large current capacity or high input voltage. There is a need for a circuit.

Specifically, in the step-down circuit, a method of controlling the current of the output terminal by controlling the current while switching the input voltage or controlling the current flowing through the direct connection of the switch in series with the LED has been used. This has the disadvantage that the circuit is complicated and power factor correction is also difficult at the AC input.

Conventional boost type or boost type circuits have been proposed with a number of methods for controlling current by connecting an LED to an output terminal, and some circuit changes have been added to improve the characteristics thereof. This structure is simplified and the output stage capacitor is eliminated, but the application method for AC input and power factor compensation function are not presented. The conventional LED driving circuit of the simplest structure is shown in FIG. 1, and the output of the boost type circuit, which is a method of charging and discharging the energy of the inductor L by turning the switch S on and off with respect to the DC input Vin. This is an example of using LEDs. As such, there have been cases in which a simple circuit structure is proposed for a DC input, but the structure to be applied in AC and the power factor correction function have not been suggested in the existing literature. In particular, there have been cases where a power factor correction LED driving circuit using an isolated flyback method has been proposed, but a general circuit structure having an output stage capacitor has also been proposed.

As such, the conventional LED driving circuit is mainly used a circuit having a capacitor at the output terminal, which is complicated by the circuit and the AC power factor compensation circuit is often required. In addition, according to the conventional control method, the output voltage control may be unnecessary, and the current control method may not be configured.

Accordingly, an object of the present invention is to solve the above-described problems, and an object of the present invention is to replace a part with an LED without an output capacitor and a rectifying diode in a basic AC / DC circuit, and to provide current through energy charging and discharging of an inductor. To provide control and output power control, and to provide an economical and reliable LED drive circuit with power factor compensation.

In the LED driving circuit having such a simple structure, when the switch does not operate, only an input voltage is applied to the LED array of the output terminal, so that no current flows due to a higher LED array voltage, and the switch operates to boost the LED array. The present invention provides a LED driving circuit having a current source having a simple structure in which voltage is applied to enable current control and illumination power control.

First, to summarize the features of the present invention, the LED driving circuit according to an aspect of the present invention, the bridge rectifying diode; An inductor connected between one terminal of an AC power source and one terminal of an input side of the bridge rectifier diode; And a switch and an LED connected in parallel between two output side terminals of the bridge rectifying diode, and the other terminal of the AC power supply is connected to the other terminal of the input side of the bridge rectifying diode.

In addition, the LED drive circuit according to another aspect of the present invention, the bridge rectifier diode is connected to both terminals of the AC power supply to both input side terminals; LEDs and inductors connected in parallel with each other; And a switch connected between one terminal of the parallel connection structure of the LED and the inductor and one terminal of the output side of the bridge rectifying diode, wherein the other terminal of the parallel connection structure of the LED and the inductor is the other terminal of the output side of the bridge rectifying diode. Characterized in that connected with.

In addition, the LED drive circuit according to another aspect of the present invention, the bridge rectifier diode is connected to both terminals of the AC power supply to both input side terminals; Flyback transformers; A switch connected in series with the primary coil of the input side of the flyback transformer; And an LED connected between both terminals of an output side secondary coil of the flyback transformer, wherein the input side primary coil of the flyback transformer connected in series and the switch are connected between both terminals of the output side of the bridge rectifier diode. It is done.

The LED includes a plurality of LED array structures connected in series, or a plurality of LEDs connected in series and a plurality of parallel connected structures.

The brightness of the LED may be adjusted by controlling the current flowing through the LED through controlling the turn-on or turn-off of the switch.

The pulse width or frequency of the switch turn-on signal is controlled so that the current flowing through the LED follows a sinusoidal current reference value in phase with the voltage phase of the AC power supply.

In addition, the LED driving circuit according to another aspect of the present invention, the first structure including a first switch and the first LED connected in series; A second structure comprising a second switch and a second LED connected in series; And an inductor connected between one terminal of an AC power source and a contact of the first switch and the first LED, wherein both ends of the first structure and the second structure are connected, and the other terminal of the AC power source. Is connected to a contact point of the second switch and the second LED.

The first LED or the second LED includes a plurality of LED array structures connected in series, or includes a structure in which a plurality of LEDs connected in series is connected in parallel.

It may include a predetermined diode (which is a general PN junction diode, not an LED) connected in series with the LED in the current flow direction of the first LED, or may include a predetermined diode connected in series with the LED in the current flow direction of the second LED. have.

The brightness of the LED may be adjusted by controlling the current flowing through the first LED or the second LED by controlling the turn-on or turn-off of the first switch or the second switch.

The pulse width or frequency of the turn-on signal of the first switch is controlled so that the current flowing through the first LED follows a sinusoidal current reference value in phase with the voltage phase of the AC power supply, and the current flowing through the second LED determines the reference value. The pulse width or frequency of the turn-on signal of the second switch is controlled to follow.

According to the LED driving circuit having a current structure of a simple structure according to the present invention, by simplifying the driving circuit for the LED emerging as a new light source in the existing lighting market, it provides a structure that is economical and reliable and can be easily mounted on the light source structure Compared with the conventional driving circuit, there is a large competitive advantage.

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. Like reference numerals in the drawings denote like elements.

2 is a view for explaining the current source LED driving circuit 10 of a simple structure for the AC input according to an embodiment of the present invention.

Referring to FIG. 2, the LED driving circuit 10 according to an embodiment of the present invention includes an AC power source Vin, an inductor L, a bridge rectifying diode 11, and a switch S. , And LEDs. The bridge rectifying diode 11 is composed of four diodes connected in parallel between a first structure in which two diodes are connected in series, and a second structure in which two other diodes are connected in series, and a contact point of two diodes of the first structure. The contacts of the two diodes of the second and second structures are the two input side terminals, and both terminals of the parallel connection are the two output side terminals.

In FIG. 2, an inductor L is connected between one terminal of the AC power supply Vin and one terminal of the input side of the bridge rectifying diode 11, and the other terminal of the AC power supply Vin is the input side of the bridge rectifying diode 11. It is connected to the other terminal. The switch S and the LED are connected in parallel between the output positive and negative terminals of the bridge rectifying diode 11. Here, the LED includes a plurality of LEDs connected in series, and in some cases, a plurality of LEDs in series may be connected in parallel.

In FIG. 2, when the switch S is turned off without performing the on / off switching operation, an input voltage is applied to the LED, and when the conduction voltage of the LED is higher, current does not flow to the LED and thus does not emit light.

When the switch S performs an on / off switching operation, energy is accumulated in the inductor L at the time of turn-on of the switch S, and the energy is turned off by the switch S. It becomes a current source during off) time and current can flow to LED to emit LED. Dimming adjustment of the brightness of the LED may be performed by controlling the current flowing through the LED through pulse width control or frequency control of the turn-on / turn-off control signal of the switch S. FIG.

In addition, the pulse width or frequency of the turn-on signal of the switch S can be controlled by using a predetermined control means so that the current flowing through the LED follows the sinusoidal current reference value in phase with the voltage phase of the AC power source Vin.

Here, additional circuits or elements may be attached between both terminals of the switch S to reduce the stress of the switch S, and high speed diodes may be used to improve the reverse recovery characteristics of the configuration of the LED (or LED array). A common PN junction diode, not an LED, can be attached to the LED in series with the LED direction (the current flow direction of the LED).

On the other hand, in the case of using an AC power source (Vin), unlike the direct current, the power factor correction should be performed, the LED driving circuit 10 according to an embodiment of the present invention, while the power factor compensation structure is possible to remove the capacitor on the LED output side It is characterized by the structure replaced by LED without output diode.

3 is a view for explaining a current source LED driving circuit 20 using a bidirectional switch according to another embodiment of the present invention.

Referring to FIG. 3, the LED driving circuit 20 according to another embodiment of the present invention replaces the bridge rectifying diodes of FIG. 2 with the switches S1 and S2 and the LEDs LED1 and LED2. The energy charging of L) occurs through the switches S1 and S2 and the discharge occurs through the LEDs LED1 and LED2. Here, the voltage of the AC power supply Vin is designed to be greater than the forward voltage of the LEDs LED1 and LED2, and the LEDs LED1 and LED2 each include a plurality of LEDs connected in series, and in some cases, a plurality of LEDs. The LEDs may have a structure in which a plurality of LED arrays connected in series are connected in parallel.

As shown in FIG. 3, the series connection structure of the first switch S1 and the first LED LED1 and the series connection structure of the second switch S2 and the second LED LED2 are connected in parallel, and the series connection structure Both ends of the positive and negative terminals are connected, and the inductor L is connected between one terminal of the AC power supply Vin and the first contact point of the first switch S1 and the first LED LED1 or the second switch S2. And a second terminal of the second LED (LED2), and the other terminal of the alternating current power supply Vin is connected to the other of the contacts.

In FIG. 3, when the switches S1 and S2 are turned off without the on / off switching operation, an input voltage is applied to the LEDs LED1 and LED2 but does not reach the LED conduction voltage. No current flows through LED2) and it does not emit light.

When the switches S1 and S2 respectively perform on / off switching operations at appropriate timings, the second switch S2 is turned on or turned on during the positive voltage (voltage greater than 0) period of the AC power source Vin. When the first switch S1 is turned on during the cathode voltage (less than zero) period of Vin, energy is accumulated in the inductor L, and the energy is turned off by the switches S1 and S2, respectively. It becomes a current source during off) time and current can flow to LED to emit LED. Dimming adjustment of the luminance of the LEDs LED1 and LED2 may be performed by controlling the first LED S through the pulse width control or the frequency control of the turn-on / turn-off control signal of the first switch S1 or the second switch S2. The current flowing through the LED1) or the second LED LED2 may be controlled.

In addition, it is possible to control the turn-on or turn-off of the first switch S1 by using a predetermined control means so that the current flowing through the first LED LED1 follows the sinusoidal current reference value in phase with the voltage phase of the AC power source Vin. In order to control the current flowing through the second LED LED2 to follow the reference value of the AC power source Vin, the control unit may control the turn-on or turn-off of the second switch S2.

Here, in order to reduce the stress of the switch S, additional circuits or elements can be attached between both terminals of the first switch S1 or the second switch S2, and the reverse of the configuration of the LED (or LED array) is possible. To improve recovery, high-speed diodes can be attached to the LED in series with the LED's direction (the current's current flow direction).

FIG. 4 is a view for explaining a current source LED driving circuit 30 in which an LED is connected to the output of the bridge rectifying diode 31 according to another embodiment of the present invention.

Referring to FIG. 4, the LED driving circuit 30 according to another embodiment of the present invention includes an AC power source Vin, an inductor L, a bridge rectifying diode 31, a switch S, and an LED. do. Here, the LED may include a plurality of LEDs connected in series, and in some cases, a plurality of LEDs may have a structure in which a plurality of LED arrays connected in series are connected in parallel.

In FIG. 4, both terminals of the AC power supply Vin and the input terminals of the bridge rectifier diode 31 are connected to each other, the LED and the inductor L are connected in parallel, and in the parallel connection structure of the LED and the inductor L. The cathode terminal of the LED is connected to the positive terminal (upper terminal) of the output side of the bridge rectifying diode 31, and the other terminal (lower anode side terminal) and the bridge rectifying diode (lower anode side terminal) of the parallel connection structure of the LED and the inductor L ( The switch S is connected between the other terminal of the output side of the terminal 31).

In Fig. 4, when the switch S is turned off without performing the on / off switching operation, since the input voltage is applied to the LED and does not reach the conduction voltage of the LED, no current flows to the LED, and thus the LED does not emit light.

When the switch S performs an on / off switching operation, energy is accumulated in the inductor L at the time of turn-on of the switch S, and the energy is turned off by the switch S. It becomes the current source which discharges during off time, and current flows to LED and can emit LED. For example, the dimming adjustment of the brightness of the LED may be performed by controlling the current flowing through the LED through the pulse width control or the frequency control of the turn-on / turn-off control signal of the switch S. In addition, the switch S may be controlled to be turned on or off using predetermined control means so that the current flowing through the LED follows the sinusoidal current reference value in phase with the voltage phase of the AC power supply Vin.

Here, additional circuits or elements may be attached between both terminals of the switch S to reduce the stress of the switch S, and a high speed diode may be used to improve the reverse recovery characteristic of the LED (or LED array) configuration. It can be attached to the LED in series with the LED direction (the current flow direction of the LED).

5 is a view for explaining the current source LED driving circuit 40 of the flyback insulated structure according to another embodiment of the present invention.

Referring to FIG. 5, the LED driving circuit 40 according to another embodiment of the present invention includes an AC power source Vin, a flyback transformer T, a bridge rectifier diode 41, and a switch S ), And LEDs. Here, the LED may include a plurality of LEDs connected in series, and in some cases, a plurality of LEDs connected in series may be connected in parallel.

In Fig. 5, both terminals of the AC power supply Vin and the input terminals of the bridge rectifying diode 41 are connected, respectively, and the input side primary of the flyback transformer T is connected between the output terminals of the bridge rectifying diode 41. The coil and the switch S are connected in series, and an LED is connected between both terminals of the secondary coil of the output side of the flyback transformer T.

In Fig. 5, when the switch S is turned off without performing the on / off switching operation, since the input voltage is applied to the LED and does not reach the conduction voltage of the LED, no current flows to the LED, and thus the LED does not emit light.

In the case where the switch S performs on / off switching operation, the energy accumulated in the primary coil of the input side of the flyback transformer T during the turn-on / turn-off of the switch S is flyback depending on the winding ratio. It is transmitted through the secondary coil of the output side of the transformer (T) so that the current can flow through the LED to emit light. For example, dimming adjustment of the brightness of the LED may be performed by controlling a current flowing through the LED through pulse width control or frequency control of the turn-on / turn-off control signal of the switch S.

At this time, the control of the turn-on / turn-off of the switch S determines a sinusoidal current reference value that is in phase with the voltage phase of the AC power source Vin, and the current flowing through the LED or the switch S follows this reference value (the same). Value) to ensure power factor correction.

In the LED driving circuit 40 as described above, the power factor correction structure is possible, and the capacitor is removed from the LED output side and has the structure of replacing the LED without the output side rectifying diode.

As described above, the present invention has been described by way of limited embodiments and drawings, but 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.

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

2 is a view for explaining a current source LED driving circuit of a simple structure for the AC input according to an embodiment of the present invention.

3 is a view for explaining a current source LED driving circuit using a bidirectional switch according to another embodiment of the present invention.

4 is a view illustrating a current source LED driving circuit in which an LED is connected to the output of a rectifying diode according to another embodiment of the present invention.

FIG. 5 is a diagram for describing a current source LED driving circuit having a flyback insulation structure according to another embodiment of the present invention.

Claims (7)

Bridge rectifying diodes; An inductor connected between one terminal of an AC power source and one terminal of an input side of the bridge rectifier diode; A switch and an LED connected in parallel between two positive and negative terminals on the output side of the bridge rectifying diode, And the other terminal of the AC power supply is connected to the other terminal of the input side of the bridge rectifier diode. A first structure comprising a first switch and a first LED connected in series; A second structure comprising a second switch and a second LED connected in series; And An inductor connected between a terminal of an AC power source and a contact of the first switch and the first LED, Both the positive and negative terminal ends of the first structure and the second structure are connected, And the other terminal of the AC power supply is connected to a contact point of the second switch and the second LED. A bridge rectifier diode having both terminals of the AC power supply connected to both terminals of the input side; LEDs and inductors connected in parallel with each other; And a switch connected between the anode terminal of the LED and the negative terminal of the output side of the bridge rectifying diode in a parallel connection structure of the LED and the inductor. And a cathode terminal of the LED having a parallel connection structure between the LED and the inductor is connected to a positive terminal of the output side of the bridge rectifier diode. A bridge rectifier diode having both terminals of the AC power supply connected to both terminals of the input side; Flyback transformers; A switch connected in series with the primary coil of the input side of the flyback transformer; And An LED connected between both terminals of the secondary coil of the output side of the flyback transformer, And an input side primary coil of the flyback transformer connected in series and the switch are connected between both terminals of an output side of the bridge rectifier diode. The method according to claim 1, 2, 3 or 4, The LED may include a plurality of LED array structures connected in series, or a plurality of LEDs connected in series includes a structure in which a plurality of LEDs connected in parallel. The method according to claim 1, 2, 3 or 4, LED driving circuit further comprises a predetermined diode connected in series to the LED in the current flow direction of the LED. The method according to claim 1, 2, 3 or 4, The control signal of the switch to control the current flowing through the LED through the pulse width control or the frequency control of the control signal of the switch to adjust the brightness of the LED and follow the sinusoidal current reference value in phase with the voltage phase of the AC power supply. LED drive circuit, characterized in that the pulse width control or frequency control.

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