KR20090001101A - Dimmer for ac driven light emitting diode - Google Patents

Abstract

A dimmer for an AC driving LED is provided to prevent minute radiation of an LED in dark change establishment by parallely connecting a parallel resistor in the LED. A rectifier(23) is serially connected to an AC power supply and an AC driving LED(21). The rectifier rectifies inputted AC voltage. A current controller(24) is connected to the rectifier. According to the establishment of the luminous output, the current controller controls the current passing through the rectifier. A parallel resistor(25) is parallely connected to the AC driving LED. The range of the parallel resistor is determined in order that the voltage of both ends of the parallel resistor is lower than turning on voltage of the AC driving LED in case the luminous output is set up as a dark change and that the voltage of both ends of the parallel resistor is higher than turning on voltage of the AC driving LED in case the luminous output is set up.

Description

Dimmer for AC Drive LED {DIMMER FOR AC DRIVEN LIGHT EMITTING DIODE}

1 is a circuit diagram illustrating an dimmer for an AC driving LED according to an embodiment of the present invention.

2 is a circuit diagram illustrating an dimmer for an AC driving LED according to another embodiment of the present invention.

3 is a circuit diagram illustrating an dimmer for an AC driving LED according to the embodiment of FIG. 2.

The present invention relates to a dimmer, and more particularly to a dimmer of a light emitting diode driven by alternating current.

Light emitting diodes are being developed to have high brightness and high power, and are being used for lighting purposes. Light emitting diodes are generally driven at a relatively low direct current (DC) in their structure, but methods such as connecting a plurality of light emitting diodes in series in a forward and reverse direction in order to directly drive a high voltage alternating current (AC) Is being developed.

In general, home and industrial lighting devices are used by connecting directly to the alternating current. Devices that attach to these lighting devices and adjust their brightness to their liking, cause the brightness to become brighter, or vice versa, are called dimmers. Dimmers not only provide a suitable lighting environment for those who use the lights, but can also extend the life of the lighting device itself.

The structure of the dimmer should be appropriately selected depending on the characteristics of the lighting device. For example, in the case of fluorescent lamps, a stepwise dimming method using a ballast is used. In the case of a direct current driving LED, a method of adjusting the output pulse width in the rectifier may be used.

Meanwhile, in the case of an incandescent lamp that emits light by heating the filament, it may be directly connected to an alternating current, and the brightness may be adjusted by using a triac element. Triacs are bidirectional power devices that can control bidirectional current communication with gate voltage.

AC-driven light-emitting diodes also connect directly to alternating current, so a triac can be applied in the same way as an incandescent lamp. In this case, only the turn-on or turn-off time of the light emitting diode can be controlled by the gate voltage of the triac, and the brightness of the triac cannot be controlled. There is a limit to control.

An object of the present invention is to provide an AC drive light emitting diode dimmer capable of adjusting the brightness of the AC drive light emitting diode.

According to an embodiment of the present invention, an AC driving light emitting diode dimmer is connected to an AC power source and an AC driving light emitting diode in series to rectify an input AC voltage, and is connected to the rectifying unit and passes through the rectifying unit according to a light emission amount setting. And a parallel resistor connected in parallel to the AC driving light emitting diode so as to adjust the magnitude of the current, wherein the magnitude of the parallel resistor includes a voltage across the parallel resistor when the amount of light emission is set to dark power. It is determined so as to be lower than the turn-on voltage of the AC driving light emitting diode, and when the amount of light emission is set, the voltage across the parallel resistor is higher than the turn-on voltage of the AC driving light emitting diode.

According to an embodiment, the rectifier may be a bridge rectifier.

According to an embodiment, the current adjusting unit may include a fixed resistor connected to one end of the rectifier, a variable resistor connected between the fixed resistor and the other end of the rectifier, and a control electrode connected to a contact of the fixed resistor and the variable resistor. The first and second electrodes may include transistors connected to one end and the other end of the rectifying unit, respectively.

In this case, the transistor may be a field effect transistor, and the variable resistor may have a variable resistance value according to the light emission amount setting.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. The same reference numerals are used for the same elements in the drawings, and duplicate descriptions of the same elements are omitted.

1 is a circuit diagram illustrating an dimmer for an AC driving LED according to an embodiment of the present invention. Referring to FIG. 1, a dimmer for an AC driving LED (hereinafter also referred to as a dimmer) 12 is connected to an AC power source AC in series with the AC driving LED 11. The dimmer 12 includes a rectifier 13 and a current controller 14.

The rectifier 13 rectifies the AC voltage applied in series via the AC driving LED 11. The rectified voltage V _R is applied to the current regulator 14.

The current regulator 14 is configured to adjust the magnitude of the current I _C flowing in the current regulator 14 according to the control signal V _C. At this time, the current I _C passing through the current controller 14 is a current output from the rectifier 13. Since the current output from the rectifier 13 is rectified by the AC current input to the rectifier 13 through the AC drive LED 11, the magnitude of the current input to the rectifier 13 and the current output from the rectifier 13. Are closely related to each other.

If the magnitude of the current output from the rectifier 13 is limited, the magnitude of the alternating current input to the rectifier 13 is also limited. That is, the magnitude of the input AC current of the rectifier 13 may also be adjusted by adjusting the magnitude of the output current of the rectifier 13. However, the magnitude of the output current of the rectifier 13 may be adjusted by the current controller 14 according to the control signal V _C.

As a result, the magnitude of the current flowing in the AC drive LED 11 is adjusted in accordance with the control signal V _C. Since the amount of light is adjusted according to the magnitude of the current passing through the AC driving LED 11, it is possible to adjust the amount of light of the AC driving LED 11 according to the control signal V _C.

2 is a circuit diagram illustrating an dimmer for an AC driving LED according to another embodiment of the present invention. Referring to FIG. 2, the AC driving LED dimmer 22 is connected to an AC driving LED 21 and an AC power source. The dimmer 22 includes a rectifier 23, a current controller 24, and a parallel resistor 25. Unlike in FIG. 1, the parallel resistor 25 is connected in parallel to the AC drive LED 21.

First, referring back to the circuit of FIG. 1, even when the current is blocked by the current control unit 24, some minute current may actually flow. When the AC power source is, for example, an AC voltage having a peak value of about 300 V, and the turn-on voltage of the AC driving LED 11 is about 100 V, the current adjusting unit 14 has an equivalent input resistance. For example, if it is 2 mA, the dimmer 12 is subjected to an alternating voltage of about 200 V, and thus, a small alternating current having a peak value of about 100 mA flows through the AC driving LED 11. Once the voltage applied to the AC drive LED 11 is equal to or higher than its turn-on voltage, the AC drive LED 11 can emit fine light even with such a current.

In general, microluminescence is not a major problem, but in some cases such microluminescence may not be suitable for the purpose of a particular lighting system. For example, microluminescence can be a significant disadvantage if the dimmer needs to completely eliminate the light emission of the luminaire, such as in a theater.

In the circuit of FIG. 2, there is a parallel resistor 25 to prevent the above-described microluminescence. The parallel resistor 25 is connected in parallel with the AC driving LED 21, the size of which is smaller than the turn-on equivalent resistance of the AC driving LED 21 and may have a size of about 1/3, for example. Therefore, the voltage across the AC drive LED 21, that is, the voltage across the parallel resistor 25 is lower than the turn-on voltage of the AC drive LED 21, and the AC drive LED 21 remains turned off. do. Even if there is a minute current in the current regulator 24, the minute currents all flow through the parallel resistor 25, so that the AC drive LED 21 can keep the turn-off state. Therefore, fine light emission can also be eliminated completely.

At this time, the value of the parallel resistor 25 is determined in consideration of the magnitude of the expected microcurrent and the turn-on voltage value of the AC driving LED.

For example, if the size of the parallel resistor 25 is too large, the magnitude of the voltage across the parallel resistor 25 may be similar to the turn-on voltage of the AC driving LED 21 even when dark power is set. The AC drive LED 21 can be turned on by the voltage across the parallel resistor 25 with only the same microcurrent, which is undesirable.

On the contrary, when the size of the parallel resistor 25 is too small, no matter how the current flowing through the current regulator 24 is increased, the voltage across the parallel resistor 25 becomes higher than the turn-on voltage of the AC driving LED 21 and finally. Until light emission occurs, only power may be consumed without the desired light emission, which is also undesirable.

Accordingly, the size of the parallel resistor 25 is a current value obtained by dividing the voltage value applied to the current regulator 24 by the equivalent input resistance value of the current regulator 24 when it is set to dark power, that is, the current regulator 24. The voltage value obtained by multiplying the value of the parallel resistor 25 by the magnitude of the microcurrent flowing in the lower than the turn-on voltage value of the AC driving LED 21 prevents the AC driving LED 21 from emitting light and starts emitting light. When it is set, the AC driving LED 21 is larger because the voltage value obtained by multiplying the value of the current flowing through the current adjusting unit 24 by the size of the parallel resistor 25 is greater than the turn-on voltage value of the AC driving LED 21. Determined within the range to be turned on. Therefore, when the dark power of the dimmer 22 is set using the parallel resistor 25, the micro-emission of the AC drive LED 2 can be prevented, and when the dimmer 22 is set to light emission, the AC drive LED 21 ) Can be emitted.

When the dimmer 22 is set to the maximum light emission amount, since most of the current supplied from the AC power flows to the AC driving LED 21, the power consumed by the parallel resistor 25 is negligible.

 FIG. 3 is a circuit diagram illustrating a dimmer for an AC driving LED of FIG. 2.

Referring to FIG. 3, the dimmer 32 for an AC driving LED includes a bridge rectifier 33, a current regulator 34, and a parallel resistor 35. The bridge rectifier 33 has four diodes connected in a ring to rectify the AC voltage, and the rectified AC voltage V _R is output from the first and second nodes N1 and N2. The current controller 34 includes a transistor 341, a fixed resistor 342, and a variable resistor 343.

The parallel resistor 35 is connected in parallel to the AC drive LED 31.

The transistor 341 may be a field effect transistor (FET), but may also be a bipolar junction transistor (BJT). Here, the case of FET will be described as an example.

The drain D of the transistor 341 is connected to the first node N1, and the source S is connected to the second node N2. A fixed resistor 342 is connected between the gate G and the drain D of the transistor 341, and the variable resistor 343 is disposed between the gate G and the source S of the transistor 341. Connected. The size of the variable resistor 343 is adjusted according to the control signal V _C electrically generated by the user, and in some embodiments, the user may manually adjust the size of the variable resistor 343.

Since the transistor 341 is an FET, the drain current is adjusted by the gate-source voltage. For example, when the transistor is an enhanced type metal oxide semiconductor FET, the drain current is given by Equation 1 below. For other types of FETs, there is a similar relationship between drain current and gate-source voltage.

At this time, I _D is a drain current, and, μ _n is the movement of Electronics, C _ox is per unit area of the gate oxide capacitance, W is the gate width, L is the gate length, V _GS is the gate-source voltage, V _th is The threshold voltage of the transistor device.

When the gate-source voltage V _GS becomes higher than the threshold voltage V _{th of the} transistor, current begins to flow in the drain. Drain current I _D increases and decreases as a function of gate-source voltage V _GS .

The rectified AC voltage V _R is divided at a ratio of the fixed resistor 342 and the variable resistor 343. Since the voltage across the variable resistor 343 is the gate-source voltage V _{GS of} the transistor 341, when the size of the variable resistor 343 is adjusted, the gate-source voltage V _GS of the transistor 341 is increased. In addition, the size of the drain current I _D of the transistor 341 may also be adjusted. Since the sum of the drain current I _D and the current flowing through the fixed resistor 342 and the variable resistor 343 is approximately equal to the current flowing through the AC driving LED 31, the size of the variable resistor 343 is eventually reduced. By adjusting, the brightness of the AC drive LED 31 can be adjusted.

The size of the parallel resistor 35 is determined similarly to the case of FIG. That is, when set to dark power, the current value obtained by dividing the voltage value across the current controller 34 by the size of the fixed resistor 341 which is the equivalent input resistance of the current controller 34 (that is, the current controller 34). The voltage value obtained by multiplying the magnitude of the parallel resistor 35 by the magnitude of the parallel resistor 35 is smaller than the turn-on voltage value of the AC driving LED 31 so that the AC driving LED 31 does not emit light (that is, (current Voltage across fixed part / fixed resistor size) × Parallel resistor size <Turn-on voltage of AC drive LED).

In addition, when it is set to emit light at a minimum, the voltage value applied to the current regulator 34 at that time is equal to the equivalent input resistance of the current regulator 34 (that is, the resistance plus the fixed resistor 342 and the variable resistor 343). Since the voltage value obtained by multiplying the current value divided by the size of the parallel resistor 35 is greater than the turn-on voltage value of the AC driving LED 31, the AC driving LED 31 should be turned on (that is, (current regulation). Voltage across both ends / (Fixed resistance + Variable resistance) x Parallel resistance size> Turn-on voltage of AC drive LED).

When the size of the variable resistor 343 is low and the gate-source voltage V _GS is lower than the threshold voltage V _{th of} the transistor 341, the transistor 341 is turned off. At this time, a fine current flows in the current adjusting unit 34 according to the size of the fixed resistor 342, but the voltage between both ends of the parallel resistor 35 generated by the minute current is higher than the turn-on voltage of the AC driving LED 31. Since it is low, the AC drive LED 31 maintains a dark state.

When the gate-source voltage V _GS becomes larger than the threshold voltage V _th of the transistor 341 by increasing the size of the variable resistor 343, current flows between the source and the drain in the transistor 341. do. A current flowing through the fixed resistor 342 and the variable resistor 343 and a current flowing through the transistor 341 flow together in the parallel resistor 35, and the magnitude of the current is larger than the micro current during the dark field. Therefore, when the size of the variable resistor 343 is increased, the voltage across the parallel resistor 35 becomes higher than the turn-on voltage of the AC driving LED 31, and the AC driving LED 31 emits light.

For example, when the AC power source is a 220V AC voltage having a maximum value of about 300V, and the turn-on voltage of the AC drive LED 31 is 100V, the parallel resistor 35 has a resistance of 300 mA and a fixed resistor 342. ) May be determined as a resistance of 2 kΩ and the variable resistor 343 as a variable resistor having a maximum size of 500 kΩ.

When the variable resistor 343 is low and the transistor 341 is turned off, that is, set to a dark power, the parallel resistor 35 is subjected to a maximum voltage of about 40V. Since the AC drive LED 31 is not turned on at such a voltage, dark power can be maintained.

When the transistor 341 is turned on by increasing the size of the variable resistor 343, the current of Equation 1 flows in the transistor 341, and thus the magnitude of the current flowing through the parallel resistor 35 is also increased. Even if the current flowing through the parallel resistor 35 increases, the AC drive LED 31 is in a dark state while the voltage across the parallel resistor 35 does not yet reach the turn-on voltage of the AC drive LED 31.

The size of the variable resistor 343 is further increased to further increase the current flowing through the transistor 341. When the current flowing through the parallel resistor 35 is greater than about 330 kHz, the voltage across the parallel resistor 35 is about. Greater than 100V, the AC drive LED 31 is finally turned on.

In some embodiments, capacitance may be further added between the first and second nodes. In this case, the rectified AC voltage will have a DC waveform with ripple, but the operation of the specific circuit is essentially the same.

Dimmer according to an embodiment of the present invention can adjust the amount of light emission of the AC drive LED only by adjusting the variable resistance, by connecting the parallel resistor in parallel to the LED to prevent the micro-light emission of the LED when setting the dark power, the dimmer itself The electric power consumption is small, the structure is simple, and it can manufacture at low cost.

Although described with reference to the embodiments above, those skilled in the art can understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention described in the claims below. will be.

Claims (5)

A rectifier connected in series with an AC power source and an AC driving light emitting diode to rectify an input AC voltage; A current adjusting unit connected to the rectifying unit and connected to adjust the magnitude of the current passing through the rectifying unit according to the emission amount setting; And A parallel resistor connected in parallel to the AC driving light emitting diode, The magnitude of the parallel resistor is such that the voltage across the parallel resistor is lower than the turn-on voltage of the AC drive light emitting diode when the amount of light emission is set to dark, and the voltage across the parallel resistor is set when the emission amount is set. An AC driving LED dimmer characterized in that it is determined within a range to be higher than the turn-on voltage of the driving LED. The AC driving light emitting diode dimmer of claim 1, wherein the rectifying unit is a bridge rectifier. The method according to claim 1, wherein the current control unit A fixed resistor connected to one end of the rectifying unit; A variable resistor connected between the fixed resistor and the other end of the rectifier; And And a control electrode is connected to the contact of the fixed resistor and the variable resistor, and the first and second electrodes comprise transistors connected to one end and the other end of the rectifying unit, respectively. 4. The AC driving light dimmer of claim 3, wherein the transistor is a field effect transistor. The AC dimmer of claim 3, wherein the variable resistor has a variable resistance value according to the light emission amount setting.

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