KR20040084512A - Traffic Signal Light Device Capable of Controlling Electric Current Through LED - Google Patents

Abstract

PURPOSE: A traffic signal light apparatus provided with a current control function by using a light emitting device(LED) is provided to maintain the luminance of the LED as well as to prevent the flicker effect. CONSTITUTION: A traffic signal light apparatus provided with a current control function by using a light emitting device(LED) includes a power circuit(110), a rectifying circuit(120), a capacitor(C1), a static voltage circuit and a light emitting circuit(130). The power circuit(110) supplies the power. The rectifying circuit(120) rectifies the AC voltage supplied from the power unit(110). The capacitor(C1) is connected to the rectifying circuit(120) in parallel. The static voltage circuit is connected to the capacitor(C1) in parallel and connected to the resistor(R1) and the Zener diode(ZD) in serial. And, the light emitting circuit(130) generates the light through a plurality of LEDs by receiving the constant voltage from the static voltage circuit.

Description

Traffic Signal Light Device Capable of Controlling Electric Current Through LED}

The present invention relates to a traffic light device using a light emitting diode (LED), and more particularly, a resistance element having a negative temperature coefficient while controlling to maintain a constant current flowing through the light emitting diode despite a change in an input voltage. The present invention relates to a traffic light apparatus using a light emitting diode to compensate for a change in brightness of a light emitting diode according to a voltage and temperature change by maintaining a constant brightness of the light emitting diode.

In recent years, light emitting diodes (LEDs) have been developed to provide accurate and safe information transmission of traffic signals in the increasingly complex and dangerous traffic environment, and to compensate for the disadvantages of energy saving in conventional incandescent bulb signals. A traffic light using Light Emitting Diode (hereinafter referred to as "LED") has appeared.

1 is a circuit diagram schematically showing the circuit configuration of a conventional traffic light device using the LED.

The traffic light device 100 using the conventional LED is a power supply unit 110 for supplying power; Rectifying unit 120 for full-wave rectifying the AC voltage supplied from the power supply unit 110; And a traffic light emitter 130 for emitting light by receiving a rectified voltage.

Traffic light emitting unit 130 in the traffic light device 100 is configured as described above is composed of a plurality of LEDs. The LED has an electrical characteristic in which a current rapidly increases as shown in FIG. 2 when a predetermined voltage or more is applied.

On the other hand, as shown in FIG. 3, the energization time of the traffic light emitting unit 130 is only about 1/3 of the power supply time from the rectifying unit 120. As such, the brightness of the LED may not be fully utilized due to the inability to continuously maintain the conduction current of the LED, thereby increasing the number of expensive LEDs in order to obtain desired illuminance.

In order to compensate for this disadvantage, in the drawing of FIG. 1, an inductor is inserted in series at a point or a smoothing capacitor is inserted in parallel between b and c to reduce the ripple included in the output voltage of the rectifier 120. Although a method of increasing the energization time of the power supply is used, the ripple of the voltage applied to the LED is not completely eliminated, which has a problem in that the effect is limited.

In addition, even if the output voltage of the rectifier 120 fluctuates up and down within a range of about 20%, the brightness of the traffic light emitter 130 is required to be kept constant to some extent, as shown in FIG. 2. Since the current has a characteristic of rapidly changing according to the change of the voltage, there is a disadvantage that the brightness deviation is severe according to the output voltage variation of the rectifier 120.

And, as shown in Figure 4, the traffic light emitting unit 130 made of LED has a characteristic that the brightness decreases as the temperature rises. When the ambient temperature rises more than twice, the brightness decreases by approximately 50%. However, there is a disadvantage that the brightness change is severe according to the temperature change.

In order to solve the above problems, the present invention controls the current flowing through the light emitting diode to be kept constant despite the change in the input voltage, while the luminance of the light emitting diode is made constant using a resistance element having a negative temperature coefficient. The purpose of the present invention is to provide a traffic light apparatus using a light emitting diode that compensates for a change in brightness of a light emitting diode according to voltage and temperature changes.

1 is a circuit diagram schematically showing the circuit configuration of a conventional traffic light device using the LED,

2 shows the voltage versus current characteristics of an LED;

3 is a view showing the waveform of the output current with respect to the input voltage applied to the LED in the conventional traffic light device,

4 is a diagram showing the temperature versus brightness characteristics of the LED,

5 is a block diagram showing a circuit configuration of a traffic light device using an LED having a current control function according to an embodiment of the present invention,

6 is a diagram illustrating an NTC resistor circuit in which a resistance value changes with temperature change.

<Description of Symbols for Main Parts of Drawings>

110: power supply unit 120: rectification unit

130: signal light emitting unit C1: condenser

R1 to R7, Rs: resistance R _N : NTC resistance

Z _D : Zener Diodes AMP: Amplifiers

MOSFET: Metal Oxide Field Effect Transistor Vz: Zener Diode Voltage

Vc: NTC voltage Vf: Amplifier output voltage

V _LED : Voltage at both ends of traffic light emitting part Vp: V1-V _LED

The present invention to achieve the above object, the power supply for supplying power; A rectifier for full-wave rectifying the AC voltage supplied from the power supply; A smoothing capacitor connected in parallel with the rectifier; A constant voltage unit connected in parallel with the smoothing capacitor and having a resistor and a zener diode connected in series; And it provides a traffic light device using an LED having a current control function characterized in that it comprises a light emitting unit for receiving a constant voltage of the constant voltage unit and emits through a plurality of light emitting diodes.

In addition, according to a second object of the present invention, there is provided a power supply unit for supplying power; A rectifier for full-wave rectifying the AC voltage supplied from the power supply; A temperature compensator having a negative temperature coefficient resistance element that receives the output of the rectifier and cancels a change in current according to a change in ambient temperature to maintain a constant output current; And it provides a traffic light device using the LED having a temperature compensation function characterized in that it comprises an LED light emitting unit for receiving the output of the temperature compensation unit and emits through a plurality of light emitting diodes.

In addition, according to a third object of the present invention, a power supply unit for supplying power; A rectifier for full-wave rectifying the AC voltage supplied from the power supply; A smoothing capacitor connected in parallel with the rectifier; A constant voltage unit connected in parallel with the smoothing capacitor and having a resistor and a zener diode connected in series; A temperature compensator having a negative temperature coefficient resistance element that receives the output of the constant voltage unit and cancels a change in current due to a change in ambient temperature to maintain a constant output current; And it provides a traffic light device using the LED having a current control function characterized in that it comprises an LED light emitting unit for receiving the output of the temperature compensation unit and emits through a plurality of light emitting diodes.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

When explaining the basic concept of the present invention.

According to the present invention, a circuit is constructed by combining a capacitor, a resistor, an amplifier, a MOSFET, and the like in parallel and directly so that a traffic light made of LED maintains a constant current flowing through the LED despite a change in voltage applied to the LED. The circuit is constructed using a negative temperature coefficient resistor to keep the current flowing through the LED constant despite changes in ambient temperature.

Here, the negative temperature coefficient resistance element will be described in more detail.

Negative Temperature Coefficient of Resistance (NTC) is a thermistor having a negative temperature coefficient among the sensors whose resistance changes when the temperature rises. NTC devices have a temperature of less than 300 ° C and usually mix two or more transition metal oxides such as Co, Mn, Cu, Fe, CuO to improve sinterability, and F ₂ O ₃ or L ₁₂ O to reduce resistance. Is a sintered body calcined at a high temperature of 1200 to 1400 ° C. by adding Cr ₂ O to increase the resistance, and the resistance has a negative temperature coefficient.

The NTC device has a large temperature coefficient of resistance to temperature, which results in good micro-temperature and precision measurements, a simple structure, and miniaturization. It is insensitive to pressure, magnetism, and other factors.

In general, the resistance of the thermistor is the no-load resistance at the standard temperature of 25 ° C. The no-load resistance is the dc resistance of the thermistor with no electrical heat dissipation at the specified temperature. In order to measure this value, the thermistor's heat dissipation should be limited so that the change of DC resistance is within ± 0.01% even if heat is generated.

The relationship between the resistance and the temperature of an NTC device having a high negative temperature coefficient in the no-load state of temperature is expressed by Equation 1.

Where R ₁ represents the resistance value at absolute temperature T ₁ (K), R ₀ represents the resistance value at absolute temperature T ₀ (K), β is the β integer, and T ₀ and T ₁ represent the absolute temperature. Indicates.

β constant is the material constant of the NTC device and is an integer indicating the magnitude of the resistance change with respect to the temperature between any two temperatures (T ₀ , T ₁ ) in the resistance-temperature characteristic, and increases slightly as the temperature increases. It depends on the temperature range. A large β constant means a large change in resistance to temperature, and unless otherwise specified, the β constant is calculated as a resistance value between 25 ° C. and 85 ° C. and depends on the composition of the material and the sintering conditions.

5 is a block diagram showing a circuit configuration of a traffic light device using an LED having a current control function according to an embodiment of the present invention.

Traffic light device 200 according to the present invention is the power supply unit 110 and the rectifier 120 and the traffic light emitting unit 130 is electrically connected, the smoothing capacitor (C1) is connected in parallel with the rectifier 120, The series connection of the resistor R1 and the zener diode Z _D is connected in parallel with the smoothing capacitor C1 and the anode of the zener diode Z _D is grounded.

In addition, the field effect transistor FET and the resistor Rs are connected in series between the traffic light emitter 130 and the ground, and one terminal of the resistor Rs is connected to the ground. An NTC resistor R _N and an amplifier AMP are connected in series between (a), which is a connection point of the resistor R1 and the zener diode Z _D , and the field effect transistor FET.

A resistor R2 is connected between the connection point (b) of the NTC resistor R _N and the amplifier AMP and ground, and a feedback resistor R4 is provided between the output terminal of the amplifier AMP and the negative input terminal. ) Is connected, and a resistor R3 is connected between the connection point (c) of the field effect transistor (FET) and the resistor (Rs) and the (-) input terminal of the amplifier (AMP).

In the above configuration, the field effect transistor (FET) is an element that controls the output current with an input voltage, and is implemented as a metal oxide semiconductor field-effect transistor (MOSFET), but with another semiconductor amplification element. It can be configured alternatively. Field effect transistors (FETs) are transistors whose input gates are insulated with a thin silicon oxide film and have a fairly high input impedance.

The amplifier AMP is an operational amplifier and has two differential inputs (+,-) and one output terminal. The amplifier (AMP) basically amplifies the difference between the voltages between the two input terminals and outputs the output.If the positive input voltage of the differential input is high, the output becomes positive, and if the input voltage is high, the output is negative. It becomes However, this results in an amplification near infinity, so if there is a differential input voltage, the output will be at the maximum of (+) or (-) and will not work as a practically usable amplifier. Therefore, the negative feedback which causes the output to be fed back to the negative input side through the resistor R4 is made to cancel the voltage difference of the differential input.

Zener diode (Z _D ) is a diode for constant voltage fabricated to exhibit operating characteristics in the breakdown region of the PN junction. By changing the doping level of the PN semiconductor is produced by the corresponding voltage to have a breakdown range of 2 ~ 200 [V]. Zener breakdown, unlike Avalanche breakdown, when the diode is strongly doped, the depletion layer becomes very narrow.When the intensity of the applied field in the depletion layer reaches 300,000 [V / cm], the valence band electrons It is pulled up sufficiently to become a conductive state. This form of surrender is referred to as high field emission. The reverse current can be ignored until the breakdown voltage Vz is reached in the characteristics of the zener diode Z _D.

As described above, the NTC resistor R _N is a resistor in which a resistance value changes according to a temperature change. The NTC resistor R _N may be described in detail with reference to FIG. 6.

As shown in FIG. 6, the NTC resistor R _N connects the resistor R5 and the resistor R7 in series between the zener voltage V _Z and the NTC voltage Vc of the zener diode Z _D. , In which the NTC R6 is connected in parallel to the resistor R5.

Next, the preferred operation of the traffic light device 200 configured as described above will be described in detail.

When AC power is supplied from the power supply unit 110, the voltage rectified by the rectifier 120 and smoothed to the capacitor C1 is applied to the series structure of the resistor R1 and the zener diode Z _D. At this time, both ends of the Zener diode _(D Z) and has a Zener voltage (V _Z) occurs, the Zener diode resistor (R1) connected in series _(D Z) is applied to the both-end voltage (V _E). Here, since the Zener voltage V _Z maintains a constant voltage even if the power supply voltage changes, the change in the power supply voltage causes a change in the voltage V _E of both ends of the resistor R1.

In FIG. 5, the voltage V1 across the capacitor C1 may be represented by Equation 2 below.

Here, V1 is the input voltage, V _LED is the voltage at both ends of the traffic light emitting unit 130, V _P is the voltage except the voltage at both ends of the traffic light emitting unit 130 from the input voltage, that is, the electric field through the resistor (Rs) at ground The voltage up to the drain of the effect transistor FET is shown.

On the other hand, the NTC voltage Vc applied to the positive input terminal of the amplifier AMP is obtained as shown in Equation (3).

The NTC voltage Vc is applied to the positive input terminal of the amplifier AMP, and the output of the output terminal of the amplifier AMP is applied to the gate terminal of the field effect transistor FET. ) Is negative feedback through the resistor (R4) to the input terminal. Therefore, the NTC voltage Vc and the voltage Vf at the connection point (c) are controlled to be similar values.

The output of the amplifier AMP is applied to the gate terminal of the field effect transistor FET, so that the field effect transistor FET is operated, so that the signal light emitting part (eg, a source of the field effect transistor FET passes through a drain). 130 flows through the current. At this time, the LED current (I _LED ) flowing to the traffic light emitting unit 130 is obtained as shown in Equation 4.

Here, for example, if Rs = 75 Ω and Vc = 3 V, the I _LED is 40 mA. It can be seen from Equation 4 that the current flowing to the traffic light emitting unit 130 can be adjusted by controlling the NTC voltage Vc.

Table 1 shows the NTC resistance value, NTC voltage (Vc), NTC voltage, the normalized value, the luminance value of the LED of the traffic light emitter 130, the final luminance value, etc. according to the temperature change obtained by the applicant through the experiment. . Table 1 shows a Zener voltage (V _Z ) of 17 V in FIGS. 5 and 6, resistance R2 of 7 KΩ, resistance R5 of 47 KΩ, resistance R7 of 20 KΩ, NTC resistance of 15 KΩ at 25 ° C. It is an experimental value when using.

division NTC (R6) R _N Vc Normalization Vc LED brightness Final brightness 25 ℃ 15 ㏀ 31.4 ㏀ 0.182 V _Z One One One 70 ℃ 3.3 ㏀ 23.1 ㏀ 0.232 V _Z 1.27 0.7 0.889 -20 ℃ 110 ㏀ 52.9 ㏀ 0.1168 V _Z 0.64 1.4 0.896

In Table 1, when the temperature is 25 ° C, the NTC voltage (Vc) is 0.182 V _Z , and thus 3.094 V, and the control current (I _LED ) is approximately 41 mA. When the temperature is 70 ° C, the NTC voltage (Vc) is 0.232 V _Z, so it is 3.944 V, and the control current (I _LED ) is approximately 52 mA. When the temperature is -20 ° C, since the NTC voltage Vc is 0.1168 V _Z , the temperature is 1.9856 V, and the control current I _LED is approximately 26 mA.

Here, when the NTC voltage (Vc) when the temperature is 25 ℃ normalized to 1, when the temperature is changed to 70 ℃, 1.27 times the LED current (I _LED ) flows, the signal light emitting unit 130 As shown in FIG. 4, the brightness of the LED shows about 70% of the performance when the temperature is 25 ° C. FIG. Therefore, the final luminance was calculated as 1.27 * 0.7 and appeared as 0.889, and the luminance was decreased by about 10% compared with the 25 ℃.

If the temperature is -20 ℃, 0.64 times the LED current (I _LED ) flows than when the 25 ℃, the brightness of the LED is about 140% performance compared to when the temperature is 25 ℃ as shown in FIG. It was increased 1.4 times, and the final luminance was calculated as 0.64 * 1.4, which is 0.896, which showed about 10% decrease in luminance compared to 25 ℃.

That is, even if the luminance characteristic varies from 70% to 140% according to the temperature change of the LED in the traffic light emitter 130, the final luminance is controlled by ± 10% by controlling the applied current using an NTC resistor having negative characteristics according to the temperature. It can be seen that it can be compensated within.

Also, even if the input voltage V1 changes, the amplifier AMP causes Vc. By being controlled to be Vf, the current is constantly controlled so that the V _LED is constant, and eventually absorbs the remaining voltage variation in the field effect transistor FET by the change in the input voltage V1.

Therefore, even if the input voltage V1 rises, only Vp rises, but the V _LED remains constant. When the temperature becomes high, the NTC voltage Vc rises due to the NTC resistor R _N. Will be done. This is because the NTC resistance (R _N ), as shown in FIG. 4, causes the resistance value to increase at low temperatures to decrease the NTC voltage (Vc), and at high temperatures, the resistance value drops to increase the NTC voltage (Vc). It is by.

According to an exemplary embodiment of the present invention, the current flowing through the light emitting diode is kept constant despite the change in the input voltage, and the luminance of the light emitting diode is kept constant by using a resistor having a negative temperature coefficient. In addition, it is possible to realize a traffic light apparatus using a light emitting diode that compensates for a change in luminance of the light emitting diode according to a change in voltage and temperature.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, the use of the zener diode and its control circuit allows the current flowing through the LED to be constantly controlled in spite of the change in the input voltage. Flicker does not occur.

In addition, by using the NTC resistive element, it is possible to compensate for the fluctuation of the brightness of the light emitting diode according to the temperature change, thereby maintaining a constant brightness.

Claims (14)

A power supply unit 110 for supplying power; Rectifier 120 for full-wave rectifying the AC voltage supplied from the power supply unit 110; A smoothing capacitor C1 connected in parallel with the rectifier 120; A constant voltage unit connected in parallel with the smoothing capacitor C1 and having a resistor R1 and a Zener diode Z _D connected in series; And The light emitting unit 130 receives the constant voltage of the constant voltage unit and emits light through a plurality of light emitting diodes (LEDs). Traffic light device using an LED having a current control function, comprising a. The method of claim 1, And an operational amplifier (AMP) for canceling the voltage difference of the differential input by negative feedback so that the differential input is output at a constant voltage. A series connection point (A) of the resistor R1 and the Zener diode Z _D is connected to a positive input terminal of the operational amplifier AMP, and an output of the operational amplifier AMP is emitted. The LED having the current control function, which is applied to the unit 130 and the output of the operational amplifier AMP is applied to the negative input terminal of the operational amplifier AMP through the resistor R4. Traffic light device. The method of claim 1, Between the output terminal of the operational amplifier (AMP) and the light emitting unit 130 is connected a metal oxide semiconductor field-effect transistor (MOSFET) for controlling the output current by the input voltage, A source of the metal oxide semiconductor field effect transistor (MOSFET) is grounded through a resistor (Rs), a drain is connected to the light emitting unit 130, and a gate is connected to an output terminal of the operational amplifier (AMP). The traffic light device using the LED having the current control function, characterized in that the (-) input terminal of the operational amplifier (AMP) and the source of the metal oxide semiconductor field effect transistor are connected via a resistor (R3). . A power supply unit 110 for supplying power; Rectifier 120 for full-wave rectifying the AC voltage supplied from the power supply unit 110; A temperature compensating unit having a negative temperature coefficient resistance element that receives the output of the rectifying unit 120 and cancels the variation of the current according to the ambient temperature change to keep the output current constant; And The LED light emitting unit 130 receives the output of the temperature compensation unit and emits light through a plurality of light emitting diodes (LEDs). Traffic light device using the LED having a temperature compensation function characterized in that it comprises a. The method of claim 4, wherein The negative temperature coefficient resistance element is a traffic light device using an LED having a temperature compensation function, characterized in that the resistance changes to a negative temperature coefficient when the temperature rises. The method of claim 4, wherein The temperature compensation unit connects a resistor (R5) and a resistor (R7) in series, and a traffic light device using an LED having a temperature compensation function, characterized in that the NTC (R6) resistor in parallel to the resistor (R5) . The method of claim 4, wherein And an operational amplifier (AMP) for canceling the voltage difference of the differential input by negative feedback so that the differential input is output at a constant voltage. An output terminal of the temperature compensator is connected to a positive input terminal of the operational amplifier AMP, an output of the operational amplifier AMP is applied to the light emitting unit 130, and an output of the operational amplifier AMP. A traffic light device using the LED having the current control function, characterized in that applied via the resistor (R4) to the negative input terminal of the operational amplifier (AMP). The method of claim 4, wherein Between the output terminal of the operational amplifier (AMP) and the light emitting unit 130 is connected a metal oxide semiconductor field-effect transistor (MOSFET) for controlling the output current by the input voltage, A source of the metal oxide semiconductor field effect transistor (MOSFET) is grounded through a resistor (Rs), a drain is connected to the light emitting unit 130, and a gate is connected to an output terminal of the operational amplifier (AMP). The traffic light device using the LED having the current control function, characterized in that the (-) input terminal of the operational amplifier (AMP) and the source of the metal oxide semiconductor field effect transistor are connected via a resistor (R3). . A power supply unit 110 for supplying power; Rectifier 120 for full-wave rectifying the AC voltage supplied from the power supply unit 110; A smoothing capacitor C1 connected in parallel with the rectifier 120; A constant voltage unit connected in parallel with the smoothing capacitor C1 and having a resistor R1 and a Zener diode Z _D connected in series; A temperature compensating unit having a negative temperature coefficient resistance element that receives the output of the constant voltage unit and cancels a change in current according to a change in ambient temperature to maintain a constant output current; And The LED light emitting unit 130 receives the output of the temperature compensation unit and emits light through a plurality of light emitting diodes (LEDs). Traffic light device using an LED having a current control function, comprising a. The method of claim 9, And an operational amplifier (AMP) for canceling the voltage difference of the differential input by negative feedback so that the differential input is output at a constant voltage. An output terminal of the temperature compensator is connected to a positive input terminal of the operational amplifier AMP, and an output of the operational amplifier AMP is applied to the LED light emitting unit 130. Traffic light device using the LED with the current control function, characterized in that the output is applied to the negative input terminal of the operational amplifier (AMP) through the resistor (R4). The method of claim 9, Between the output terminal of the operational amplifier (AMP) and the LED light emitting unit 130 is connected a field effect transistor (MOSFET) for controlling the output current by the input voltage, The source of the field effect transistor (MOSFET) is grounded through a resistor (Rs), the drain is connected to the LED light emitting unit 130, the gate is connected to the output terminal of the operational amplifier (AMP) And (-) input terminal of the operational amplifier (AMP) and a source of the field effect transistor are connected via a resistor (R3). The method of claim 11, The field effect transistor (FET) is a metal oxide semiconductor field effect transistor (MOSFET: Metal-Oxide Semiconductor Field-Effect Transistor) characterized in that the traffic light device using an LED having a current control function. The method of claim 9, An NTC voltage Vc is generated in the temperature compensator, and the negative temperature coefficient resistance element increases the resistance value at a low temperature so that the NTC voltage Vc decreases. A traffic light device using the LED having the current control function, characterized in that Vc) is increased. The method of claim 9, The negative temperature coefficient resistance element is connected to the resistor (R5) and the resistor (R7) in series, the NTC (R6) resistor connected in parallel to the resistor (R5) characterized in that the LED having a current control function Used traffic light device.