KR100385145B1 - Switched Mode Power Supply Circuit for Driving LED - Google Patents

Abstract

The switched mode power supply circuit for driving a light emitting diode of the present invention has an object to block the pulsed voltage, improve the power factor, and compensate for the temperature characteristics of the light emitting diode so as to operate regardless of weather changes.

In order to achieve this, the switched mode power supply circuit for driving a light emitting diode of the present invention includes: power supply means for inducing a DC voltage from a primary coil part to a secondary coil part according to a switching operation of a MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And a plurality of series connected resistors are connected in parallel between the control signal generating means and the load terminal, and are connected between an output ground line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series connected resistors. It is characterized in that it comprises a reference voltage generating means including a resistance element that is connected in parallel with the resistor and the resistance value varies with temperature changes.

Description

Switched Mode Power Supply Circuit for Driving LEDs

The present invention relates to a switched mode power supply circuit, and more particularly, to a switched mode power supply circuit for driving a light emitting diode used in a traffic light.

Vehicle and pedestrian traffic lights, which are widely used to date, have used a 120 watt [W] light bulb as a light source for traffic lights. By the way, this light bulb is not only consumes a lot of power, but also has a short lifespan, making it difficult to manage and maintain.

Therefore, in recent years, as the production of light emitting diodes (LEDs) is diversified due to the development of semiconductor technology, light emitting diodes that consume less than 1/10 of the power required to obtain the same illuminance compared to general light bulbs are used for vehicles and walking. The trend is applied to traffic lights.

However, in order to drive a signal lamp using a light emitting diode, a separate power supply device is required. That is, the conventional light bulb uses a 220 volt AC power source, so a separate power supply is unnecessary. However, since the light emitting diode uses a DC power source, the 220 volt commercial power is rectified to DC, and the rectified DC voltage Switching mode power supply (hereinafter referred to as 'SMPS') is required to convert DC into DC voltage of required size.

On the other hand, in a traffic light using a conventional light bulb, the triac is turned on and off to control the magnitude of the input voltage. When the turn-off signal is input to the triac gate, the triac anode and the triac are turned on and off. No current flows between the cathodes, but a pulsating voltage of 130-150 volts is applied. This is due to the capacitance characteristics present in the triac even when the turn-off signal is input to the triac's gate. When the triac is connected to the SMPS, the SMPS operates instantaneously due to the pulsed voltage. It may cause a minute flickering and may cause a traffic accident.

In addition, SMPS converts the rectified DC voltage into a DC voltage of a required size by controlling the duty ratio by controlling the on-off time of the transistor, which has a disadvantage of very low power factor. SMPS, which is used to drive traffic lights installed in a semiconductor, is sensitive to temperature because semiconductors are used.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a switched mode power supply circuit for driving a light emitting diode to cut off a pulsed voltage.

Another object of the present invention is to provide a switched mode power supply circuit for driving a light emitting diode capable of improving power factor.

Another object of the present invention is to provide a switched mode power supply circuit for driving a light emitting diode capable of compensating for temperature characteristics of the light emitting diode so as to operate regardless of a change in weather.

1 is a first embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention;

Figure 2 is a second embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention,

3 is a detailed configuration diagram of the controller U3 used in FIGS. 1 and 2;

4 is a third exemplary embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention;

5 is a view showing a fourth embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention;

6 is a fifth exemplary embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention;

Explanation of symbols on the main parts of the drawings

100: overcurrent and overvoltage protection unit 200: rectifier

300: power supply unit 400: control signal generator

500: control unit 600: power factor adjustment unit

700: pulse voltage prevention unit 800: reference voltage generation unit

The switched mode power supply circuit for driving a light emitting diode of the present invention for achieving the above object comprises: power supply means for inducing a DC voltage from a primary coil portion to a secondary coil portion in accordance with a switching operation of a MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And a plurality of series connected resistors are connected in parallel between the control signal generating means and the load terminal, and are connected between an output ground line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series connected resistors. It is characterized in that it comprises a reference voltage generating means including a resistance element that is connected in parallel with the resistor and the resistance value varies with temperature changes.

In addition, the switched mode power supply circuit for driving a light emitting diode of the present invention comprises: power supply means for inducing a DC voltage from a primary coil portion to a secondary coil portion in accordance with a switching operation of a MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And a plurality of series-connected resistors connected in parallel between the control signal generating means and the load end, and connected between an output supply line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. It is characterized in that it comprises a reference voltage generating means including a resistance element which is connected in series with the resistance to change the resistance value in accordance with the temperature change.

Preferably, the resistance element used herein is characterized in that the negative temperature coefficient thermistor.

Preferably, the switched mode power supply circuit for driving a light emitting diode of the present invention comprises: an overcurrent and overvoltage protection means in which a fuse, a varistor, and a line filter are connected in series to block an overcurrent and an overvoltage of an AC power input; And rectifying means composed of bridge diodes for converting the AC power into direct current.

In addition, the switched mode power supply circuit for driving a light emitting diode according to another aspect of the present invention includes: power supply means for inducing a DC voltage from a primary coil part to a secondary coil part according to a switching operation of a MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And a plurality of series-connected resistors connected in parallel between the control signal generating means and the load end, and connected between an output supply line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. It is characterized in that it comprises a reference voltage generating means including a resistance element that is connected in parallel with the resistance to vary the resistance value in accordance with the temperature change.

In addition, the switched mode power supply circuit for driving a light emitting diode according to another aspect of the present invention includes: power supply means for inducing a DC voltage from a primary coil part to a secondary coil part according to a switching operation of a MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And a plurality of series-connected resistors connected in parallel between the control signal generating means and the load terminal, and connected between an output grounding line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. It is characterized in that it comprises a reference voltage generating means including a resistance element which is connected in series with the resistance to change the resistance value in accordance with the temperature change.

Preferably, the resistance element used herein is characterized in that the positive temperature coefficient thermistor.

Preferably, the over-current and over-voltage protection means connected to the fuse, the varistor and the line filter in series to block the over-current and over-voltage of the AC power input; And rectifying means composed of bridge diodes for converting the AC power into direct current.

In addition, the switched mode power supply circuit for driving a light emitting diode of another invention of the present application includes power supply means for inducing a DC voltage from the primary coil portion to the secondary coil portion in accordance with the switching operation of the MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And a plurality of series-connected resistors connected in parallel between the control signal generating means and the load end, and connected between an output supply line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. A resistance element that is connected in series with a resistor to change a resistance value according to a temperature change, and parallel with a resistor connected between an output grounding line and a part which draws a reference voltage output to the control signal generating means among the plurality of resistors connected in series; And a reference voltage generating means including a resistance element connected to and varying the resistance value according to the temperature change.

Preferably, the resistance element that varies the resistance value according to the temperature change in the reference voltage generating means is characterized in that the negative temperature coefficient thermistor.

Preferably, the over-current and over-voltage protection means connected to the fuse, the varistor and the line filter in series to block the over-current and over-voltage of the AC power input; And rectifying means composed of bridge diodes for converting the AC power into direct current.

Here, the above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a first embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention.

The first embodiment of the switched mode power supply circuit for driving a light emitting diode according to the present invention is an overcurrent and overvoltage protection unit 100 formed of a fuse, a varistor, and a line filter to protect the SMPS from the overcurrent and overvoltage of an AC power input. In order to convert an AC voltage into a DC voltage, switching of a transistor provided on the primary side of the rectifier 200 made of a bridge diode and the rectified voltage input through the rectifier 200 to supply a signal lamp (load) using a light emitting diode. The power supply unit 300 to induce the secondary side according to the operation, the control signal generator 400 for generating a control signal from the photodiode to control the duty ratio of the transistor, and the control signal output from the control signal generator The magnitude of the voltage received through the phototransistor and induced to the secondary side of the power supply unit 300 The control unit 500 for adjusting, the power factor adjusting unit 600 connected to the primary side of the power supply unit for adjusting the power factor of the power supply unit, and is connected between the rectifier 200 and the power supply unit 300 to control the pulse voltage. And a portion for drawing out the reference voltage output to the control signal generator 400 while the pulsation voltage prevention unit 700 and the plurality of resistors connected in series between the control signal generator 400 and the load terminal are connected in parallel. And a reference voltage generator 800 including a negative temperature coefficient thermistor connected in parallel with a first resistor connected between the output ground lines.

In the first embodiment of the present invention having the above configuration, it is used to drive a signal light composed of a plurality of red light emitting diodes or a signal light composed of a plurality of yellow light emitting diodes, which will be described below.

The varistor in the overcurrent and overvoltage protection unit 100 flows a surge that can be input from the AC power supply to ground to prevent the SMPS from being affected, and the line filter of the reactance component is an overcurrent component. In this way, the rectifier 200 rectifies the AC voltage input through the overcurrent and overvoltage protection unit 100 into a DC voltage.

The first thermistor (TH1, NTC thermistor) in the power supply unit 300 is initially short-circuited because there is no charge charged in the capacitor C1 connected in parallel with the rectifier 200, so that the capacitor C1 Infinite inrush current that can flow is prevented, but after a certain time has passed, once the capacitor (C1) is charged, the first thermistor generates heat according to the current flowing through the first thermistor, and thus the temperature of the first thermistor As a result, the resistance value of the negative temperature coefficient thermistor becomes very small. That is, the first thermistor is used to prevent inrush current due to the application of AC power.

Here, the capacitor C1 has a very small capacitance and absorbs noise of the AC current with little influence on the initial current.

On the other hand, the current passing through the diode D5 is prevented from rapid rise by the inductor (L2) and is charged to the capacitor (C3) through the primary side (T1) of the power supply unit 300, the diode (D5) for blocking As a result, when the MOSFET in the controller U1 is turned off, the voltage due to the increase in the transformer voltage of the power supply unit 300 is prevented from being reversely charged to the capacitor C1. The diode D6 is also prevented from flowing back to the inductor L2 when the MOSFET in the controller U1 is turned off for blocking purposes. When the MOSFET in the controller U1 is turned on, the charging voltage of the capacitor C3 is induced to the secondary side T4 by a current flowing through the primary sides T1 and T2 of the power supply unit 300.

Here, the inductor L2 in the power factor adjusting unit 600 is associated with the capacitor C1 to improve the power factor. The inductance of the reactor L2 is increased, and the capacitance of the capacitor C1 is reduced. In the related art, since the capacitors C2 and C3 and the resistor R2 and the uppermost primary side do not exist in the power factor adjusting unit 600, the capacitance of the capacitor C1 has to be increased. The capacitance of C1) can be made small, and the power factor can be improved.

The capacitor C2 in the power factor adjusting unit 600 is used for a snubber, and the capacitor C3 uses a nonpolar coupling capacitor, which is required due to the nature of a signal lamp when using a polar capacitor. Due to the repeated on-off caused by the breakdown of the insulation can be solved a frequent problem.

The transient diode TD1 of the pulse voltage suppressor 700 blocks the voltage when the voltage across the capacitor C5 connected in parallel with the primary side T3 of the power supply unit 300 in a line filter is higher than a predetermined level. The voltage preventing diode, and the resistor R1 of the pulse voltage suppressor 700 is initially used only to charge the capacitor C5 with the time constant R1 * C5, and after the capacitor C5 is charged Unused starting resistor.

The controller U1 in the control unit 500 is a pulse width modulation chip, and the width of the pulse varies according to the change in the turn-on time of the photo transistor U2.

The negative temperature coefficient thermistor TH3 in the reference voltage generator 800 becomes smaller as the temperature increases. When the resistance value decreases, the combined resistance value with the resistor R10 connected in parallel becomes smaller, and the reference voltage Vref applied between the ground and the portion from which the reference voltage output to the control signal generator 400 is drawn is also smaller. You lose.

The turn-on time of the controller U3 in the control signal generator 400 increases, and thus, the turn-on time of the photodiode U2-1 also increases, and the pulse width of the controller U1 in the controller 500 extends. As a result, the output voltage outputted to the load stage is increased to increase the drive voltage of a signal lamp using a red light emitting diode or a yellow light emitting diode that is applied to the load stage.

Meanwhile, the capacitors C7 and C8 and the inductor L3 of the secondary side are used as the LC filter, and the reference voltage extracting part of the reference voltage generator 800 uses the variable resistor VR1, which is a reference voltage at room temperature. This allows you to adjust (Vref).

2 is a second embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention.

According to a second embodiment of a switched mode power supply circuit for driving a light emitting diode according to an embodiment of the present invention, an overcurrent and overvoltage protection unit 100 including a fuse, a varistor, and a line filter to protect the SMPS from an overcurrent and an overvoltage of an AC power input may be provided. In order to convert an AC voltage into a DC voltage, switching of a transistor provided on the primary side of the rectifier 200 made of a bridge diode and the rectified voltage input through the rectifier 200 to supply a signal lamp (load) using a light emitting diode. The power supply unit 300 to induce the secondary side according to the operation, the control signal generator 400 for generating a control signal from the photodiode to control the duty ratio of the transistor, and the control signal output from the control signal generator The magnitude of the voltage received through the phototransistor and induced to the secondary side of the power supply unit 300 The control unit 500 for adjusting, the power factor adjusting unit 600 connected to the primary side of the power supply unit for adjusting the power factor of the power supply unit, and is connected between the rectifier 200 and the power supply unit 300 to control the pulse voltage. And a portion for drawing out the reference voltage output to the control signal generator 400 while the pulsation voltage prevention unit 700 and the plurality of resistors connected in series between the control signal generator 400 and the load terminal are connected in parallel. And a reference voltage generator 800 including a negative temperature coefficient thermistor connected in series with a second resistor connected between the output supply lines.

That is, the portion different from the first embodiment of the present invention is connected to the upper end of the portion where the negative temperature coefficient thermistor TH2 in the reference voltage generator 800 draws the reference voltage output to the control signal generator 400. It is connected in series with the second resistor, which is suitable for driving a signal lamp using a green light emitting diode which has a high possibility of malfunction in cold weather such as winter when the temperature drops below freezing in a configuration for compensating the temperature at low temperature. .

The operation of the different parts will be described as follows.

The negative temperature coefficient thermistor TH2 in the reference voltage generator 800 has a large resistance value as the temperature decreases. As the resistance value increases, the combined resistance value of the series-connected resistor R9 becomes larger, and the reference voltage Vref applied between the ground and the portion from which the reference voltage output to the control signal generator 400 is drawn becomes smaller. do.

Therefore, the turn-on time of the controller U3 in the control signal generator 400 increases, the turn-on time of the photodiode U2-1 also increases, and the pulse width of the controller U1 in the controller 500 extends. As a result, the output voltage outputted to the load stage is increased to increase the driving voltage of the signal lamp using the green light emitting diode at the load stage.

FIG. 3 is a detailed configuration diagram of the controller U3 used in FIGS. 1 and 2, and since the components are generally used, a separate description thereof will be omitted.

4 is a third embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention.

A third embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention controls a constant temperature coefficient thermistor to be used as a driving circuit such as a signal using a yellow light emitting diode or a red light emitting diode, which causes degradation in heat. The third resistor R9 connected in parallel between the portion for drawing the reference voltage output to the signal generator 400 and the output supply line is used in parallel.

Due to the characteristics of the constant temperature coefficient thermistor, the resistance value increases as the temperature increases, so that the combined resistance value of the parallel-connected resistor R9 and the constant temperature coefficient thermistor TH4 becomes larger, so that the reference voltage Vref becomes lower. . Subsequent operations in the control signal generator 400 and the controller 500 are the same as in the above-described embodiment.

5 is a fourth embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention.

According to a fourth embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention, a constant temperature coefficient thermistor is used as a control signal generator so that it can be used as a driving circuit for a signal lamp using a green light emitting diode, which has a performance deterioration during a cold weather. It is used by connecting in series with the fourth resistor R10 connected between the part which draws the reference voltage output to 400) and the output ground line.

As the temperature decreases due to the characteristics of the constant temperature coefficient thermistor, the resistance decreases, so that the combined resistance of the series-connected resistor R10 and the constant temperature coefficient thermistor TH5 decreases, so that the reference voltage Vref decreases. . Subsequent operations in the control signal generator 400 and the controller 500 are the same as in the above-described embodiment.

6 is a fifth embodiment of a switched mode power supply circuit for driving a light emitting diode according to the present invention.

The fifth embodiment of the switched mode power supply circuit for driving a light emitting diode according to the present invention is a combination of the first embodiment and the second embodiment, and a yellow light emitting diode or a red light emitting diode in which a performance decrease occurs in a heat and cold period. The negative temperature coefficient thermistor is connected in series with the fifth resistor (R9) connected between the part which draws the reference voltage output to the control signal generator 400 and the output supply line so that it can be used as a driving circuit of a signal lamp using The sixth resistor R10 connected in parallel between the part which draws the reference voltage output to the control signal generator 400 and the output ground line is used.

The negative temperature coefficient thermistor (TH6) connected in series with the fifth resistor (R9) and the negative temperature coefficient thermistor (TH7) connected in parallel with the sixth resistor (R10) are lower than the resistance value at room temperature (about +25 degrees Celsius). At higher temperatures (about +70 degrees Celsius), the resistance increases, and at higher temperatures (about 30 degrees Celsius), the resistance is reduced. That is, at high temperature, the change in the resistance value of the negative temperature coefficient thermistor TH7 may have more influence on the reference voltage Vref than the change in the resistance value of the negative temperature coefficient thermistor TH6. The resistance value is appropriately adjusted so that the change in the resistance value of thermistor TH6 may have more influence on the reference voltage Vref than the change in the resistance value of the negative temperature coefficient thermistor TH7. Subsequent operations in the control signal generator 400 and the controller 500 are the same as in the above-described embodiment.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is also possible that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

According to the configuration as described above, the present invention is compared to the driving circuit for traffic lights using the light emitting diodes of the present invention, the signal light using the green, red, yellow light emitting diodes do not unnecessarily flicker, the power factor is improved, regardless of weather changes This has the beneficial effect of allowing it to operate normally.

Claims (11)

Power supply means for inducing a DC voltage from the primary coil portion to the secondary coil portion in accordance with the switching operation of the MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And A plurality of resistors connected in series are connected in parallel between the control signal generating means and the load terminal, and a resistor is connected between an output ground line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series connected resistors. A reference voltage generating means including a resistance element connected in parallel with and varying a resistance value according to a temperature change Switched mode power supply circuit for driving a light emitting diode comprising a. Power supply means for inducing a DC voltage from the primary coil portion to the secondary coil portion in accordance with the switching operation of the MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And A plurality of series-connected resistors are connected in parallel between the control signal generating means and the load end, and are connected between an output supply line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. Reference voltage generating means including a resistance element connected in series with a resistor to change a resistance value according to a temperature change Switched mode power supply circuit for driving a light emitting diode comprising a. The method according to claim 1 or 2, The resistance element is a switch mode power supply circuit for driving a light emitting diode, characterized in that the negative temperature coefficient thermistor. The method of claim 3, Overcurrent and overvoltage protection means in which a fuse, a varistor, and a line filter are connected in series to block overcurrent and overvoltage of an input AC power source; And Rectifying means composed of bridge diodes for converting the AC power into direct current Switched mode power supply circuit for driving a light emitting diode further comprising. Power supply means for inducing a DC voltage from the primary coil portion to the secondary coil portion in accordance with the switching operation of the MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And A plurality of series-connected resistors are connected in parallel between the control signal generating means and the load end, and are connected between an output supply line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. Reference voltage generating means including a resistance element connected in parallel with a resistor to change the resistance value according to temperature change Switched mode power supply circuit for driving a light emitting diode comprising a. Power supply means for inducing a DC voltage from the primary coil portion to the secondary coil portion in accordance with the switching operation of the MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And A plurality of series-connected resistors are connected in parallel between the control signal generating means and the load end, and are connected between an output grounding line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. Reference voltage generating means including a resistance element connected in series with a resistor to change a resistance value according to a temperature change Switched mode power supply circuit for driving a light emitting diode comprising a. The method according to claim 5 or 6, The resistor element is a switch mode power supply circuit for driving a light emitting diode, characterized in that the constant temperature coefficient thermistor. The method of claim 7, wherein Overcurrent and overvoltage protection means in which a fuse, a varistor, and a line filter are connected in series to block overcurrent and overvoltage of an input AC power source; And Rectifying means composed of bridge diodes for converting the AC power into direct current Switched mode power supply circuit for driving a light emitting diode further comprising. Power supply means for inducing a DC voltage from the primary coil portion to the secondary coil portion in accordance with the switching operation of the MOS transistor in the following control means; Control signal generation means connected to the secondary coil of the power supply means for generating a control signal for controlling the duty ratio of the MOS transistor; The MOS transistor is connected to a first coil part of the primary coil part of the power supply means to receive a control signal output from the control signal generating means and to adjust the magnitude of the voltage induced in the secondary coil part of the power supply means. Control means for controlling the switching of the; A power factor adjusting means connected to a second coil part of the primary coil part of the power supply means to adjust the power factor of the power supply means; Ripple voltage preventing means connected to the first coil part of the power supply means to block the pulse voltage; And A plurality of series-connected resistors are connected in parallel between the control signal generating means and the load end, and are connected between an output supply line and a portion for drawing a reference voltage output to the control signal generating means among the plurality of series-connected resistors. A parallel connection with a resistor connected between a resistor connected to the resistor and having a different resistance value according to a temperature change, and a part connected to the output grounding line and a portion of the series connected resistor to draw the reference voltage output to the control signal generating means. Reference voltage generating means including a resistance element that varies in resistance according to temperature change Switched mode power supply circuit for driving a light emitting diode comprising a. The method of claim 9, A switch mode power supply circuit for driving a light emitting diode according to claim 1, wherein the resistance element whose resistance is changed in accordance with the temperature change in the reference voltage generating means is a negative temperature coefficient thermistor. The method of claim 10, Overcurrent and overvoltage protection means in which a fuse, a varistor, and a line filter are connected in series to block an overcurrent and an overvoltage of an input AC power source; And Rectifying means composed of bridge diodes for converting the AC power into direct current Switched mode power supply circuit for driving a light emitting diode further comprising.