KR100959376B1 - Power supply for led traffic light able to adjust brightness - Google Patents

Abstract

The present invention provides a power supply for an LED signal lamp capable of adjusting the brightness by outputting two constant voltages corresponding to the type of input voltage.

In accordance with an aspect of the present invention, there is provided a power supply for an LED signal lamp having a brightness control, comprising: a protection circuit unit for preventing overcurrent and / or overvoltage included in an AC power input; A rectifier for rectifying the output of the protection circuit; A power supply unit including a transformer to induce the rectified voltage output from the rectifying unit to the secondary side; A power factor adjusting unit connected to the primary side of the transformer to adjust the power factor of the power supply unit; An on-off control signal generator configured to generate an on-off control signal according to a comparison between the input AC voltage and the reference voltage of the AC power supply; A secondary rectifier for rectifying the voltage induced on the secondary side of the transformer; An output voltage adjusting unit controlled by the on-off control signal to adjust an output voltage of the output terminal by adjusting a resistance value of the output terminal; A secondary voltage feedback unit including a second photo diode having a different amount of light according to a change in an output current output to the secondary side of the transformer; And a PWM signal generator for controlling a duty ratio of the PWM signal in response to a change in the amount of light output from the second photodiode.

Description

POWER SUPPLY FOR LED TRAFFIC LIGHT ABLE TO ADJUST BRIGHTNESS}

The present invention relates to a power supply for LED traffic lights, and more particularly to a power supply for LED traffic lights that can adjust the brightness.

LED (Light Emitting Diode) traffic light is a high efficiency product with less than 15W of power consumption compared to incandescent signal light, and has an energy saving effect of about 80 to 90% at the same brightness. In addition, the LED traffic light is almost semi-permanent with a lifespan of 10 times or more compared with a conventional incandescent signal light, has a very low heat loss due to heat generation and has a light loss by using a colorless lens by emitting a specific monochromatic light.

LED traffic lights with these features and advantages are now gradually replacing incandescent signals in accordance with the national policy of energy saving.

In general, the LED signal lamp according to the prior art adopts a power supply method called switching mode power supply (SMPS) to the AC voltage applied from the LED signal controller to improve the stability of the power supply. However, such a SMPS power system has a complex structure in which a plurality of transformers, capacitors, and resistors are mounted in a complicated structure, and thus, the manufacturing cost is high, and the durability of the transformer or capacitor is degraded due to electrical fatigue load. There is a problem that is required.

In addition, the LED signal light according to the prior art with excellent visibility is not provided with a dimming function to lower the brightness at night operation, there is a disadvantage that the driving or driving disturbance caused by glare, thereby causing unnecessary power loss.

In order to solve such a problem, a number of control circuits for LED traffic lights having a dimming control function have recently been proposed.

1 is a block diagram of a control circuit for LED traffic light with a dimming control function according to the prior art, Figure 2 is a detailed circuit diagram of a control circuit for LED traffic light with a dimming control function according to the prior art.

As shown in the drawings, the power supply device 2 for the LED signal lamp according to the prior art is the rectifier 10, the voltage detector 20, the constant voltage holding unit 30, the temperature compensation unit 40, the load control unit 50 And a dummy load 60.

The rectifier 10 is a portion to which the driving power from the traffic signal controller 1 is input and is located at the tip of the power supply device.

The voltage detecting unit 20 detects the voltage rectified by the rectifying unit 10 and the detected voltage is not a normal voltage (leak current is generated due to line aging and poor construction, and a weak current for detecting whether a traffic light controller is opened or closed). Etc.) and the voltage supply to the LED traffic light 3 is cut off.

The constant voltage holding unit 30 maintains the voltage rectified by the rectifying unit at an appropriate voltage.

The temperature compensator 40 relatively compensates for the current change characteristic of the LED due to the temperature change to control the amount of current.

One end of the dummy load 60 is connected to the output terminal of the rectifier 10, and the other end thereof is connected to the output terminal of the control switch 57 of the load control unit 50.

The load controller 50 is electrically connected to the rectifier 10 and the dummy load 60, and analyzes the waveform of the voltage rectified by the rectifier 10 to analyze the waveform of the voltage in the dummy load 60 when the waveform is a normal lighting signal. Is controlled so that the current flows into the dummy load 60 only when the waveform is a dimming control signal.

In more detail, the load controller 50 includes an auxiliary power supply 51, a pulse converter 53, a waveform detector 55, and a control switch 57.

The auxiliary power supply 51 supplies a DC power to the load control unit 50 by lowering the voltage rectified by the rectifier 10 and converting the voltage to a constant voltage. As shown in FIG. 2, the auxiliary power supply unit 51 includes a resistor R13 connected to a point B and dropping a voltage of 300V to 12V, and a zener diode Z8 and a capacitor C2 connected in series with a resistor R13 to maintain DC12V. do.

The pulse converter 53 converts the voltage rectified by the rectifier 10 into a pulse-shaped square wave. The pulse converter 53 reduces the rectified voltage input from the point A (output terminal of the rectifier 10) through a resistor R14. Then convert to square wave.

The waveform detector 55 detects the discharge time of the square wave converted by the pulse converter 53, and when the discharge time is greater than or equal to the reference value, determines the dimming control signal and outputs a first control signal. The off time is less than or equal to the reference value. In this case, it is determined that the normal lighting signal and the second control signal is output. More specifically, the diodes D3 and D4 are combined with a resistor and a capacitor C3 to form a charge / discharge circuit. When the square wave applied from the pulse converter 53 is a normal lighting signal (propagation signal), the interval between the pulses and the pulses (Pause period) is short, the discharge time is short and the HIGH signal (second control signal) is output. When the square wave is the dimming control signal (half wave signal), the interval between pulses (pulse period) is long and the LOW signal 1 control signal) is output.

When the LOW signal is input from the waveform detector 55, the control switch 57 is turned on when the switch Q4 is turned on to flow a current to the dummy load 60, and when the HIGH signal is input from the waveform detector 55, the dummy switch is turned off. The load 60 is cut off so that no current flows.

However, since the LED signal lamp is directly connected to the input side, the light quantity of the LED signal lamp also changes as the input voltage changes. In other words, the domestic commercial AC voltage is regulated as 220 volts, but depending on the situation, the input voltage is varied from 190 to 250 volts. According to the control circuit as shown in FIG. As a result, the voltage applied to the LED signal lamp is also affected in proportion to the input voltage which is severely changed, and thus, the amount of light of the LED signal lamp also changes.

The present invention has been made in order to solve the above problems is an object of the present invention to provide a power supply for brightness control LED signal light.

In addition, another object of the present invention is to provide a power supply for LED signal lamps capable of controlling brightness by outputting two constant voltages corresponding to the type of input voltage.

In accordance with an aspect of the present invention, there is provided a power supply for an LED signal lamp having a brightness control, comprising: a protection circuit unit for preventing overcurrent and / or overvoltage included in an AC power input; A rectifier for rectifying the output of the protection circuit; A power supply unit including a transformer to induce the rectified voltage output from the rectifying unit to the secondary side; A power factor adjusting unit connected to the primary side of the transformer to adjust the power factor of the power supply unit; An on-off control signal generator configured to generate an on-off control signal according to a comparison between the input AC voltage and the reference voltage of the AC power supply; A secondary rectifier for rectifying the voltage induced on the secondary side of the transformer; An output voltage adjusting unit controlled by the on-off control signal to adjust an output voltage of the output terminal by adjusting a resistance value of the output terminal; A secondary voltage feedback unit including a second photo diode having a different amount of light according to a change in an output current output to the secondary side of the transformer; And a PWM signal generator for controlling a duty ratio of the PWM signal in response to a change in the amount of light output from the second photodiode.

Preferably, when the magnitude of the voltage output from the rectifier is less than a predetermined value may further include a low voltage blocking unit for blocking the control power supply voltage applied to the PWM signal generating unit.

Preferably, the on-off control signal generation unit, Comparator for comparing the input AC voltage and the reference voltage; A switching element switched according to the output signal of the comparator; And a first photodiode turned on and off according to the switching of the switching element.

Preferably, the output voltage control unit, the first photo transistor coupled in pairs with the first photo diode; A variable resistor connected to the output terminal in series with the first photo transistor; And a first resistor connected in parallel with the first photo transistor and a variable resistor.

Preferably, the secondary voltage feedback unit, a second photo diode coupled in parallel to the secondary side of the transformer; And a second resistor coupled to the second photodiode in parallel, wherein the second photodiode may vary the amount of light corresponding to the magnitude of the output current flowing through the output terminal.

Preferably, the PWM signal generation unit, the second photo transistor to vary the magnitude of the current passing in response to the change in the amount of light of the second photodiode; And a PWM controller controlling the duty ratio of the PWM signal in proportion to the magnitude of the current passing through the second photo transistor.

Preferably, full-wave rectification of a commercial AC voltage or half-wave rectification of a commercial AC voltage is applied to the input of the protection circuit unit.

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According to the present invention, it is possible to provide a power supply for LED signal lamps with adjustable brightness, and in particular, it is possible to provide a power supply for LED signal lamps with adjustable brightness by outputting two constant voltages corresponding to the type of input voltage.

Hereinafter, exemplary embodiment (s) of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, many specific details are shown in the following description, which is provided to help a more general understanding of the present invention, and the present invention may be practiced without these specific details. Will be self-evident. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Figure 3 is a detailed circuit diagram of the power supply for the brightness adjustable LED traffic light according to an embodiment of the present invention.

The power supply for the brightness adjustable LED signal lamp according to an embodiment of the present invention, the protection circuit 110, rectifier 120, power supply 130, PWM signal generator 140, low voltage cut-off unit 150, The power factor adjusting unit 160, the secondary rectifier 170, the secondary voltage feedback unit 180, the output voltage controller 190, and the on / off control signal generator 200 are included.

The protection circuit unit 110 includes a fuse, a varistor, and a line filter to protect against overcurrent and overvoltage, and to remove electromagnetic waves from an applied AC voltage. The varistor in the protection circuit unit 110 sends 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 suppresses the overcurrent component. .

The rectifier 120 rectifies the voltage output from the protection circuit unit 110 and may take the form of a bridge diode.

The power supply unit 130 includes a transformer to induce the rectified voltage output from the rectifier 120 to the secondary side according to the switching operation of the PWM signal generator 140 provided on the primary side. The first thermistor (TH1, NTC thermistor) in the power supply unit 130 is initially short-circuited because there is no charge charged in the capacitor C1 connected in parallel with the rectifier 120, and thus the capacitor C1 Infinite inrush current that can flow is prevented, but after a certain period of time, once charged in the capacitor (C1), the first thermistor generates heat according to the current flowing through the first thermistor, so that 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 130, 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 130 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 by the current flowing through the primary side of the power supply 130.

The power factor adjusting unit 160 is connected to the transformer primary side of the power supply unit 130 to adjust the power factor of the power supply unit 130. Here, the inductor L2 in the power factor adjusting unit 160 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. Conventionally, since the capacitors C2 and C3, the resistor R2 and the uppermost primary side do not exist in the power factor adjusting unit 160, the capacitance of the capacitor C1 has to be increased, but by adding them, the capacitance of the capacitor C1 may be increased. Capacitance can be made smaller and power factor can be improved.

The capacitor C2 in the power factor adjusting unit 160 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 it can solve the problem of frequent failures.

The on-off control signal generator 200 includes a first photodiode UA2A that is turned on and off according to a comparison of an applied AC voltage and a reference voltage to generate an on-off control signal.

Specifically, the OP AMP UA1 compares an AC voltage applied to the non-inverting terminal (+) with a reference voltage applied to the inverting terminal (−), and when the AC voltage is greater than the reference voltage, generates an “H” signal. If it is smaller than this reference voltage, the "L" signal is output, and the PNP transistor TR1 is turned off by the "H" signal and turned on by the "L" signal.

That is, when the input alternating voltage is 220 volts, the OP AMP outputs a "H" signal and the PNP transistor TR1 is turned off, so the first photodiode UA2A is turned off. When the input alternating voltage is 110 volts, the OP AMP is turned off. Since the PNP transistor TR1 is turned on by outputting the "L" signal, the first photodiode UA2A is turned on.

The secondary rectifier 170 rectifies and filters the voltage induced on the secondary side.

The output voltage adjusting unit 190 is controlled by the on-off control signal to adjust the output voltage of the output terminal by adjusting the output terminal resistance. Specifically, when an input alternating voltage of 110 volts is applied, the first phototransistor UA2B is turned on according to the turn-on of the first photodiode UA2A, so that the combined resistance values of the resistor R9 and the variable resistor RA7 connected in parallel are applied. The corresponding voltage is applied to the output stage. On the other hand, when an input alternating voltage of 220 volts is applied, the first photo transistor UA2B is turned off according to the turn-off of the first photodiode UA2A, so that a voltage corresponding to the resistor R9 is applied to the output terminal.

As a result, a lower voltage is output when the voltage is 110 volts compared with the case where the input alternating voltage is 220 volts. For example, 22 volts may be output when the input alternating voltage is 220 volts, and 14 volts may be output when the input alternating voltage is 220 volts.

Here, by adjusting the resistance value of the variable resistor RA7, the output voltage when the input alternating voltage is 110 volts can be adjusted. Accordingly, the amount of light of the LED signal lamp coupled to the output terminal can be controlled.

The secondary voltage feedback unit 180 includes a second photodiode U2-1 that varies the amount of light according to the variation of the output current output to the secondary side of the transformer.

In detail, when the output current flowing through the LED signal lamp coupled to the output terminal is increased, the current flowing through the second photodiode U2-1 operating in the active region is decreased, thereby reducing the amount of light of the second photodiode U2-1. When the output current flowing through the LED signal lamp coupled to the output terminal decreases, the current flowing through the second photodiode U2-1 increases, thereby increasing the amount of light of the second photodiode U2-1.

The PWM signal generator 140 controls the duty ratio of the PWM signal in response to a change in the amount of light output from the second photodiode U2-1.

Specifically, when the amount of light of the second photodiode U2-1 decreases, the current flowing through the second phototransistor U2 in the PWM signal generator 140 decreases, which is the duty ratio of the switching element in the controller U1. Reduce the duty ratio of the PWM signal.

On the other hand, when the amount of light of the second photodiode U2-1 increases, the current flowing through the second phototransistor U2 increases to increase the duty ratio of the switching element in the controller U1, thereby increasing the duty ratio of the PWM signal.

When the magnitude of the voltage output from the rectifying unit drops below a predetermined value, the low voltage blocking unit 150 blocks the control power supply voltage from being applied to the PWM signal generating unit 140. For example, when the output voltage of the rectifier 120 is 60 volts or less, the control power supply voltage Vcc is blocked from being applied to the PWM signal generator 140.

As described above, although the specific embodiment (s) have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiment (s), but should be defined by the appended claims and equivalents thereof.

1 is a block diagram of a control circuit for an LED traffic light with a dimming control function according to the prior art,

2 is a detailed circuit diagram of a control circuit for an LED traffic light with a dimming control function according to the prior art, and

Figure 3 is a detailed circuit diagram of the power supply for the brightness adjustable LED traffic light according to an embodiment of the present invention.

* Brief description of the main parts of the drawing *

110: protection circuit 120: rectifier

130: power supply unit 140: PWM signal generating unit

150: low voltage breaking unit 160: power factor adjustment unit

170: secondary rectifier 180: secondary voltage feedback

190: output voltage adjusting unit 200: on-off control signal generating unit

Claims (8)

A protection circuit unit for preventing overcurrent and / or overvoltage included in an input AC power source; A rectifier for rectifying the output of the protection circuit; A power supply unit including a transformer to induce the rectified voltage output from the rectifying unit to the secondary side; A power factor adjusting unit connected to the primary side of the transformer to adjust the power factor of the power supply unit; An on-off control signal generator configured to generate an on-off control signal according to a comparison between the input AC voltage and the reference voltage of the AC power supply; A secondary rectifier for rectifying the voltage induced on the secondary side of the transformer; An output voltage adjusting unit controlled by the on-off control signal to adjust an output voltage of the output terminal by adjusting a resistance value of the output terminal; A secondary voltage feedback unit including a second photo diode having a different amount of light according to a change in an output current output to the secondary side of the transformer; And PWM signal generator for controlling the duty ratio of the PWM signal in response to the change in the amount of light output from the second photodiode Brightness adjustable power supply for LED traffic lights including a. The method of claim 1, A low voltage blocking unit for blocking a control power supply voltage from being applied to the PWM signal generating unit when the magnitude of the voltage output from the rectifying unit is equal to or less than a predetermined value; Brightness adjustable LED signal power supply further comprising a. The method of claim 2, wherein the on-off control signal generator, A comparator comparing the input alternating voltage with a reference voltage; A switching element switched according to the output signal of the comparator; And A first photodiode on and off according to the switching of the switching element Brightness adjustable power supply for LED traffic lights including a. The method of claim 3, wherein the output voltage adjusting unit, A first photo transistor coupled in pairs with the first photo diode; A variable resistor connected to the output terminal in series with the first photo transistor; And A first resistor connected in parallel with the first photo transistor and a variable resistor Brightness adjustable power supply for LED traffic lights including a. The method of claim 3, wherein the secondary voltage feedback unit, A second photodiode coupled in parallel to the secondary side of the transformer; A second resistor coupled to the second photodiode in parallel; The second photodiode is a power supply for a brightness controllable LED signal light, characterized in that the amount of light varies in response to the magnitude of the output current flowing through the output terminal. The method of claim 5, wherein the PWM signal generation unit, A second photo transistor configured to vary a magnitude of a current passed in response to a change in the amount of light of the second photo diode; And PWM controller for controlling the duty ratio of the PWM signal in proportion to the magnitude of the current passing through the second photo transistor Brightness adjustable power supply for LED traffic lights including a. The method of claim 1, The power supply for the brightness adjustable LED signal lamp, characterized in that the full-wave rectification of commercial AC voltage or half-wave rectification of commercial AC voltage is applied to the input of the protection circuit. delete

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