KR20110005559A - Power supply unit with flicker prevention circuit for light emitting diode - Google Patents

Abstract

PURPOSE: A light emitting diode power supply apparatus equipped with a flicker removing circuit is provided to prevent the instant black out of a light emitting diode module during instant drop of an input voltage as well as preventing the instant surge of the light emitting diode module during instant rise of the input voltage. CONSTITUTION: A rectifier receives the AC or DC voltage and rectifies AC current into the DC current. A switching mode power supplier converts the DC current outputted from the rectifier into the voltage of rectangular shape. The switching mode power supply unit supplies the output DC current voltage to a load including a light emitting diode array(R3).

Description

Power Supply Unit with Flicker Prevention Circuit for Light Emitting Diodes

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for a light emitting diode having a flicker removal circuit for removing a flicker phenomenon, which is an illumination flicker phenomenon caused by an unstable power supply.

Light Emitting Diode (LED) is a type of diode that emits light when current flows. When a forward voltage is applied to an electrode of a light emitting diode (LED) formed by bonding a p-type semiconductor and an n-type semiconductor to each other, The holes are diffused into the n region and the plurality of electrons are diffused into the p region. When the electrons and the holes recombine with each other near the junction, light having a wavelength corresponding to the energy gap is emitted. At this time, the wavelength of the emitted light depends on the material used, and in general, the light emitting efficiency of the direct transition semiconductor is excellent.

Light emitting diodes have the advantages of fast response speed, low power consumption, and very long life (about 1 million hours) due to the characteristics of semiconductors.Lights using light emitting diodes (LED lighting) generate very little heat and reach almost 100%. It has high light efficiency and manufacturing cost is very low, so it is attracting attention as a light source of electronic display parts and advanced lighting of various electronic products.

Currently, light emitting diodes are generally used in mobile phones or displays, but as research on high power light emitting diodes is conducted, it is expected to replace existing fluorescent or halogen lamps in the near future.

High power high power light emitting diodes have been used as a light source for lighting, and switched power supplies have been used to efficiently drive such high power high power light emitting diodes.

1 is a configuration of a conventional LED power supply unit (PSU) using a PWM / SMPS method, the circuit structure has a simple advantage, but the power factor is disadvantageous disadvantage, Figure 2 using the PFC-PWM / SMPS method In one configuration of a conventional power supply unit (PSU) for LEDs, the power factor is 90% or more, but the circuit is complicated and expensive.

Such a conventional power supply unit cannot prevent flicker, which is a phenomenon of flickering lights, and particularly, lighting devices installed in mobile devices such as subway trains with unstable power supply have a high frequency of flicker.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a power supply device for a light emitting diode that prevents the flicker phenomenon of the illumination including the light emitting diode when the power is supplied unstable.

The light-emitting diode power supply device provided with the flicker elimination circuit according to the present invention includes a rectifier unit for applying an AC or DC voltage and rectifying current to a direct current, and a pulse width modulation (PWM) circuit. A power supply for a light emitting diode (LED) including a switching mode power supply (SMPS) for converting the input DC voltage output from the rectifier to a predetermined output DC voltage, the rectifying unit A first end connected between a switching mode power supply for supplying a predetermined voltage to a load including a plurality of light emitting diode (LED) arrays and receiving a positive output of the first output; resistance; A first Zener diode connected in series with the first resistor; A first capacitor connected in series with the first zener diode and having one end connected to a negative output of the rectifier; A light emitting device connected in series between a node between the first zener diode and the first capacitor and a negative output of the rectifier; A transistor provided in series between the other end of the load and a ground voltage source connected at one end thereof to an output of the switching mode power supply unit; One end is connected to the output of the switching mode power supply unit through a third resistor, and the other end of the transistor is connected to the gate of the transistor, and receives light generated by the light emitting device to receive the output of the switching mode power supply unit and the transistor. A light receiving element for making a low impedance path (current moving path) between gates; And a second capacitor provided in series between an output of the switching mode power supply unit and the ground voltage source.

In particular, the power supply device for a light emitting diode having the flicker removing circuit according to the present invention further includes a second resistor connecting a node between the first zener diode and the first capacitor and an anode of the light emitting device.

In particular, a light emitting diode power supply device having the flicker elimination circuit according to the present invention includes a fourth resistor connecting the light receiving element, the node between the transistors, and the ground voltage source, and the node between the third resistor and the light receiving element. And a second zener diode connecting the ground voltage source.

The first zener diode is characterized in that a cathode is connected to the first resistor, and an anode is connected to the first capacitor.

Preferably, the light emitting device is a light emitting diode, and the light receiving device is a bipolar transistor that is turned on by receiving light.

The switching mode power supply unit converts and outputs an input DC voltage output from the rectifier into a predetermined output DC voltage to provide a predetermined output DC voltage to a load including a plurality of light emitting diode (LED) arrays. It is preferable to further include a power factor correction (PFC) circuit.

The power supply device for a light emitting diode according to the present invention prevents flicker, which is a flicker of light caused by unstable supply of power, and at the moment of rising of an input voltage, a light emitting diode module having one or more LEDs connected in series / parallel is instantaneously. It prevents the light from turning on and prevents the light emitting diode module from turning off instantaneously when the input voltage falls momentarily.

Hereinafter, a power supply device for a light emitting diode of the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided by way of example so that the spirit of the invention to those skilled in the art can fully convey. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms. Also, throughout the specification, like reference numerals designate like elements.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

Figure 3 is an example showing the configuration of a power supply for a light emitting diode having a flicker removal circuit according to the present invention.

The rectifying unit receives an AC or DC voltage to rectify the current into a direct current, and the switching mode power supply unit receives an input direct current voltage output from the rectifying unit and converts it into a square wave voltage, and then outputs a predetermined output controlled through a filter. It generates DC voltage and keeps output DC voltage stable through feedback control circuit.

The switching mode power supply unit supplies an output DC voltage to a load including a plurality of light emitting diode (LED) arrays, wherein the load is a plurality of multi-chip LEDs are connected in series or in parallel or in parallel, The plurality of one-chip light emitting diodes may be connected in series or in parallel.

As shown in FIG. 3, the switch mode power supply unit includes a pulse width modulation (PWM) circuit, and the input DC voltage is a predetermined output DC voltage through a DC-DC converter using a pulse width modulation method. Is changed.

In this case, the switch mode power supply unit preferably further includes a power factor correction (PFC) circuit for improving power efficiency.

The rectifying unit and the switch mode power supply unit may be a general rectifying unit and a normal switch mode power supply unit used in a power supply unit (PSU) for supplying power to a light emitting diode module.

As shown in FIG. 3, the flicker removal circuit included in the power supply device for a light emitting diode according to the present invention includes at least two resistors R1 and R3, at least two capacitors C1 and C2, and at least one zener diode. ZD1, at least one transistor (FET) and an opto-isolator composed of a light emitting element (primary) and a light receiving element (secondary).

In detail, the first resistor R1, the first zener diode ZD1, and the first capacitor C1 are sequentially connected to each other in series, and one end of the first resistor R1 is connected to the positive output of the rectifying unit. One end of the first capacitor C1 is connected to the negative output of the rectifier.

A light emitting element (primary), which is a primary side of the opto isolator, is provided between a node between the first zener diode ZD1 and the first capacitor and a negative output of the rectifier.

Preferably, the light emitting device (primary) is a light emitting diode, and an anode of the light emitting diode is connected to a node between the first zener diode ZD1 and the first capacitor C1, The cathode is connected to the negative output of the rectifier and the cathode.

A transistor (FET) serving as a switch is provided between the load receiving the output DC voltage from the switching mode power supply and the ground voltage source.

When the transistor FET is turned on, a current movement path is formed between the load and the ground voltage source so that the light emitting diode of the load can emit light.

A gate of the transistor FET is connected to a light receiving element (secondary), which is a secondary side of the opto isolator, and the light receiving element (secondary) is output of the switching mode power supply unit through a third resistor (R3). Connected with

The light receiving element (secondary) receives light generated from the light emitting element (primary), and forms a channel having a low impedance current path by light reception. The light receiving element (secondary) is preferably a bipolar transistor (BJT) to form a channel by light reception.

When a channel is formed in the light receiving element (secondary), the output DC voltage output from the switching mode power supply unit passes through the channel of the third resistor (R3) and the light receiving element (secondary) to the gate of the transistor (FET). Is applied to turn the transistor on.

When the light emitting device (primary) of the opto isolator does not generate light, the output DC voltage of the switching mode power supply unit is not applied to the gate of the transistor (FET), and the transistor is turned off.

A second capacitor C2 is provided between the output of the switching mode power supply and the node between the load and the ground voltage source. The second capacitor self-discharges when the output DC voltage output from the switching mode power supply unit falls, thereby supplying a stable output DC voltage to the load.

As described above with reference to FIG. 3, the flicker removal circuit provided in the power supply device for a light emitting diode includes a first resistor R1 having one end connected between a switching mode power supply and a positive output of the rectifier, A first Zener diode ZD1 connected in series with a first resistor R1, a first capacitor C1 connected in series with the first Zener diode ZD1, and connected to a negative output of the rectifier, and the first capacitor A light emitting device (primary) connected in series between a node between a first Zener diode and the first capacitor and a negative output of the rectifier; an anode between the first Zener diode ZD1 and the first capacitor C1 ) Is connected, the light emitting device (primary) is connected to the negative output and the cathode of the rectifier (cathode), the output is provided in series between the other end of the load and the ground voltage source connected to one end of the output of the switching mode power supply Being One end is connected to the output of the switching mode power supply unit through a FET and a third resistor, and the gate and the other end of the transistor FET are connected to receive light generated from the light emitting device (primary). And a second capacitor C2 provided in series between the output of the switching mode power supply and the output of the transistor (FET), the light receiving element (secondary) and the output of the switching mode power supply and the ground voltage source. It is configured to include).

When AC or DC power is supplied to the rectifier, when AC DC power is supplied, a positive voltage (high potential voltage) output from the rectifier is emitted through the first resistor R1 and the first zener diode ZD1. A channel is formed in the light receiving element (secondary) supplied to the element primary and receiving light generated from the light emitting element primary.

The output DC voltage output from the switching mode power supply unit receiving the positive voltage output from the rectifier is applied to the load and is simultaneously passed through the third resistor R3 and the light receiving element (secondary) to the transistor (FET). Is applied to the gate of to turn on the transistor (FET).

When the instantaneous drop of the power supply voltage supplied to the rectifying unit occurs due to the instability of the power supply, the voltage transfer is caused by RC constant by internal resistance of the first capacitor C1 and the light emitting element (primary) itself. Delayed to prevent the instantaneous turn off of the serial / parallel connected LEDs provided in the load.

When an instantaneous increase in the power supply voltage supplied to the rectifier occurs due to instability of the power supply, voltage transfer is delayed due to the RC constant by the first capacitor C1 and the first resistor R1, and thus the load is delayed. Instantaneous turning on of the provided parallel / parallel LED is prevented.

As described above, the second capacitor C2 is a capacitor having a large charge capacity, and serves to supply a stable voltage to the load even when the output DC voltage output from the switching mode power supply unit is shaken.

Figure 4 is another example showing the configuration of a power supply for a light emitting diode having a flicker removal circuit according to the present invention. As shown in FIG. 4, the flicker removal circuit provided in the power supply device for a light emitting diode according to the present invention further includes a second resistor R2, a fourth resistor R4, and a second zener diode ZD2. do.

The second resistor R2 is provided in series between the node between the first zener diode ZD1 and the first capacitor C1 and the light emitting element (primary), and the fourth resistor R4 is received by the light receiver. It is provided in series between the gate of the element (secondary) and the transistor (FET) and the ground voltage source.

The second zener diode ZD2 is provided in series between a node between the third resistor R3 and the light receiving element (secondary) and a ground voltage source.

Similar to the first zener diode ZD1 where the cathode is connected to the first resistor R1 and the anode is connected to the first capacitor C1, the cathode of the second zener diode ZD2 is connected to the third resistor (R1). And an anode of the second zener diode ZD2 is connected to a ground voltage source.

The second zener diode ZD2 protects the light receiving element (secondary) and the transistor (FET) so that an overvoltage is not applied to the light receiving element (secondary) of the opto-isolator and the gate of the transistor (FET). do.

The second resistor R2 plays a role similar to the internal resistance of the light emitting device (primary), and in detail, the internal resistance of the first capacitor (C1) and the light emitting device (primary) itself and the second resistance. The voltage transfer is delayed by the RC constant by the resistor to prevent the momentary power off of the serial / parallel connected LEDs provided in the load.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all of the equivalents or equivalents of the claims as well as the claims to be described later will belong to the scope of the present invention. .

1 is an example showing the configuration of a conventional LED power supply using a PWM / SMPS method,

Figure 2 is an example showing the configuration of a conventional LED power supply using a PFC-WM / SMPS method,

Figure 3 is an example showing the configuration of a power supply for a light emitting diode having a flicker removal circuit according to the present invention,

Figure 4 is another example showing the configuration of a power supply for a light emitting diode having a flicker removal circuit according to the present invention.

* Description of the symbols for the main parts of the drawings *

R1 ~ R4: Resistor C1 ~ C2: Capacitor

ZD1 ~ ZD2: Zener Diode FET: Transistor

1st light emitting element 2nd light receiving element

Claims (6)

AC or DC voltage is applied, and rectifier (Rectifier) for rectifying the current to DC, Pulse Width Modulation (PWM) circuit and converts the input DC voltage output from the rectifier to a predetermined output DC voltage output In the power supply for a light emitting diode (LED) comprising a switching mode power supply (SMPS) unit, One end is connected between a switching mode power supply and a positive output of the rectifier for supplying a predetermined voltage to a load including a plurality of light emitting diode (LED) arrays by receiving the positive output of the rectifier. First resistance; A first Zener diode connected in series with the first resistor; A first capacitor connected in series with the first zener diode and having one end connected to a negative output of the rectifier; A light emitting device connected in series between a node between the first zener diode and the first capacitor and a negative output of the rectifier; A transistor provided in series between the other end of the load and a ground voltage source having one end connected to an output of the switching mode power supply; One end is connected to the output of the switching mode power supply unit through a third resistor, and the other end of the transistor is connected to the gate of the transistor, and receives light generated by the light emitting device to receive the output of the switching mode power supply unit and the transistor. A light receiving element for creating a low impedance path between gates; And a second capacitor provided in series between the output of the switching mode power supply and the ground voltage source. Power supply device for a light emitting diode provided with a flicker removal circuit comprising a. The method of claim 1, The light emitting diode power supply device And a second resistor connecting the node between the first zener diode and the first capacitor and the anode of the light emitting element. The method according to claim 1 or 2, The light emitting diode power supply device And a fourth resistor connecting the node between the light receiving element and the transistor and the ground voltage source, and a second zener diode connecting the node between the third resistor and the light receiving element and the ground voltage source. Power supply. The method according to claim 1 or 2, The first zener diode has a cathode connected to the first resistor, and an anode connected to the first capacitor. The method according to claim 1 or 2, The light emitting device is a light emitting diode, and the light receiving device is a bipolar transistor (BJT) power supply device for a light emitting diode, characterized in that. The method according to claim 1 or 2, The switching mode power supply unit further comprises a power factor correction (PFC) circuit.

Images