KR100973910B1 - Driving mechanism for led lighting - Google Patents

Abstract

PURPOSE: A device is provided to extend the lifespan of LED(Light Emitting Diode) illumination by the removal of a converter. CONSTITUTION: A rectifier circuit(200) rectifies an AC voltage into a DC voltage. An LED(600) emits light with the output of the rectifier circuit. A recoverable fuse is arranged between a rectifier circuit and a LED in order to seclude an excess current. The recoverable fuse comprises a first and a second PTC(Positive Temperature Coefficient) thermistor and a negative temperature coefficient thermistor. The second PTC thermistor and the negative temperature coefficient PTC thermistor are serially connected. The first PTC thermistor is connected to the second PTC thermistor and the negative temperature coefficient thermistor in parallel.

Description

LED lighting driving device {Driving mechanism for LED lighting}

The present invention relates to an LED lighting driving apparatus, and more particularly, to an LED lighting driving apparatus capable of removing a converter by using a PTC and exhibiting the stability of the use environment.

In the lighting field, a lighting device using a light emitting diode (LED) as a light source is rapidly spreading in place of a conventional halogen, incandescent lamp, and fluorescent lamp. LED lighting is not only more energy efficient than traditional lamps and fluorescent lamps, but also has a long life and environmentally friendly light source. Although the production cost is still more expensive than fluorescent lamps and traditional lamps, due to these advantages, research into light emitting diodes is being actively conducted.

Elements that must be provided in the light emitting diode lighting device include a light emitting diode circuit module part, a luminaire part, a converter (ballast), and the like. The converter has a variety of roles such as rectifying the voltage input from AC to DC voltage, adjusting the voltage to a voltage suitable for a lighting device, removing EMI, correcting the power factor, and protecting the surge voltage. do. As a result, the converter's own power consumption is about 10-20%.

However, due to its size, such a converter is not only troublesome to install a light emitting diode lamp, but the life of the converter itself is much shorter than that of the light emitting diode. It is inconvenient to replace.

In particular, the issues that have recently been pointed out as a stability problem of converters are causing a number of problems such as the inability to receive radio broadcasts in the LED lighting environment, the inability to operate radio equipment for ships, and the occurrence of noise when using a mobile phone.

An attempt has been made to integrate the light emitting diode driving circuit to remove such a converter, but there is a difficulty in preventing damage to the light emitting diode due to an overcurrent in the circuit. In other words, in order to commercialize the light emitting diode lighting, it is necessary to provide a lighting device capable of stably emitting light to a constantly changing external environment. However, it is difficult to commercialize the light emitting diode because it cannot guarantee stability in a state where overcurrent may damage the light emitting diode.

There is a technology that does not constitute a converter, but Korean Laid-Open Patent Publication No. 2001-0093337, but when applied to a residential light emitting diode lighting device in practice, there is a side that is difficult to operate normally due to circuit damage when an unstable condition, in particular over current flows.

On the other hand, if a fuse is installed in the LED driving circuit to protect the LED as another solution, the LED may be protected, but if the fuse is blown, there is a problem in that the entire circuit must be manufactured by an expert. In order to increase the inconvenience of customers, a constant temperature coefficient thermistor (PTC Thermistor) may be configured to act as a fuse in the circuit module. There is a problem that does not perform properly. That is, according to the change of the external environment, the intensity of illumination is suddenly weakened or the light does not emit at all, which is a fatal problem that impairs stability.

Therefore, there is an urgent need for a method of ensuring the stability of such LED lighting.

In order to solve the above problems, an object of the present invention is to provide an LED lighting driving circuit that can be operated stably while removing the converter.

In order to achieve the above object, the present invention, a varistor that can protect the rectifier circuit and the LED circuit when the abnormal voltage or abnormal current occurs; A rectifier circuit for receiving an AC voltage and rectifying it with a DC; LED for emitting light by receiving the output of the rectifier circuit; PTC for blocking the overcurrent flowing to the LED between the rectifier circuit and the LED; And a controller for controlling a power source for driving the LED, wherein the LED has a maximum ambient temperature and a minimum ambient temperature preset in the controller when the normal input current is In and the maximum allowable current is Im. Provided is an LED lighting drive whose hold current Ih is In < Ih < Im at temperature.

The LED lighting driving device may further include a resistor for voltage sharing with the LED.

In another embodiment, a rectifier circuit for receiving an AC voltage and rectifying to DC; LED for emitting light by receiving the output of the rectifier circuit; And a recoverable fuse section for blocking an overcurrent flowing to the LED between the rectifier circuit and the LED, wherein the recoverable fuse section includes a second PTC and a negative temperature coefficient thermistor connected in series. Provided are an LED lighting drive in which a first PTC is connected in parallel to a 2 PTC and a negative temperature coefficient thermistor.

In the LED, when the normal input current is In and the maximum allowable current is Im, the hold current Ih2 of the second PTC at the preset maximum ambient temperature is In <Ih2 <Im, and the first PTC's at the preset minimum ambient temperature is It is preferable that the hold current Ih1 is In &lt; Ih1 &lt; Im.

Further, it is more preferable that the hold current Ih1 of the first PTCC is Ih1 &lt; In and the hold current Ih2 of the second PTCC is Ih2 &gt; Im at the preset maximum ambient temperature.

On the other hand, the (-) temperature coefficient thermistor may be a CTI (CTR) that the electrical resistance is rapidly lowered between the predetermined maximum ambient temperature and the minimum ambient temperature.

According to the present invention, by eliminating the converter, the configuration is simplified and the service life of the LED light can be extended.

In addition, the present invention suggests a method of stably driving the LED lighting device even if the converter is removed.

And, it proposes what is the factor for driving the LED lighting device stably with the minimum unit price.

1 is a configuration diagram showing the configuration of the LED lighting drive apparatus according to the present invention;
FIG. 2 is a circuit diagram showing a configuration of an LED driving unit of the LED lighting driving device according to FIG. 1; FIG.
Figure 3 is a graph showing the electrical resistance value of the poly switch with temperature (Tyco Electronics Inc. manual);
Figure 4 is a graph showing the hold current value of the poly switch with temperature (Tyco Electronics Inc. manual);
5 is a graph showing hold current values of two poly switches according to ambient temperature;
6 is a graph showing the hold current value of the poly switch according to the ambient temperature;
7 is a circuit diagram illustrating another embodiment of the LED driver.

The configuration and operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, the LED lighting apparatus according to the present invention includes a controller 100, a power supply 110, and an LED lighting driver 120.

The controller 100 stores data necessary for driving the LED, and performs control for efficiently driving the LED. That is, the control is performed to adjust the illuminance of the LED, and the duty control is performed to adjust the on / off of the LED at a constant ratio.

The control unit 100 is provided with a power switch 102 and the ambient temperature input unit 104. The ambient temperature input unit 104 is a device configured to input a maximum ambient temperature and a minimum ambient temperature, which will be described later, and the controller 100 stores the maximum ambient temperature and the minimum ambient temperature. According to product specifications, the maximum ambient temperature and the minimum ambient temperature may be fixedly stored in the controller 100 without the ambient temperature input unit 104.

The power supply unit 110 mainly serves to supply AC power of 110V or 220V. In addition, the LED lighting driver 120 receives power from the power supply unit 110 and transmits the light to the LED which is a light emitting device.

Referring to Figure 2, the basic configuration of the LED driving unit according to the present invention will be described.

The LED driver according to the present exemplary embodiment includes a rectifier circuit 200, a varistor 500, a positive temperature coefficient 300, a resistor 400, and an LED part 600.

The rectifier circuit 200 converts AC power into DC power. The rectifier circuit 200 has a variety of short-wave rectifier circuits, but in this embodiment, a bridge rectifier circuit is used.

The bridge rectifier circuit includes four nodes 210, 220, 230, and 240 and four diodes 250, 260, 270, and 280, and the first node 210 and the third node 230 are electrically connected to the AC power source 110. In addition, the second node 220 and the fourth node 240 is connected to the LED unit 600.

The first diode 250 is provided between the first node 210 and the second node 220 to transmit a signal of the second node 220 to the first node 210. The second diode 260 is provided between the second node 220 and the third node 230 to transmit a signal of the second node 220 to the third node 230, and the third diode 270 is It is provided between the third node 230 and the fourth node 240 to transmit a signal of the third node 230 to the fourth node 240. Finally, the fourth diode 280 is provided between the first node 210 and the fourth node 240 to transmit a signal of the first node 210 to the fourth node 240.

When the first node 210 becomes a positive potential and the third node 230 becomes a negative potential by the AC power supply 110, the positive potential of the first node 210 may cause the fourth diode 280. The LED is applied to the fourth node 240 and the positive potential applied to the fourth node 240 is applied to the LED unit 600 so that the LED emits light.

On the contrary, when the third node 230 becomes the positive potential and the first node 210 becomes the negative potential, the positive potential of the third node 230 is the fourth node 240 through the third diode 270. When the positive potential applied to the fourth node 240 is applied to the LED unit 600, the LED emits light.

Meanwhile, the output from the fourth node 240 is applied to the LED unit 600 via the PTC 300, the resistor 400, and the constant current device 500.

On the other hand, the varistor 500 is connected in parallel to the input power source, is provided between the power supply and the rectifier. The varistor 500 serves to protect the light emitting diode module 600 when a voltage surge occurs due to a lightning strike. That is, the varistor 500 normally does not flow due to a high resistance, but when the voltage rises, the resistance decreases, so that when the voltage surge occurs, the current flows through the varistor 500, so that the LED module 600 Protected.

That is, in the light emitting diode lighting apparatus according to the present embodiment, when the overvoltage is input due to a surge such as an ESD or lightning strike, the varistor 500 has an infinitely large resistance under normal conditions, but when the overvoltage is introduced, the resistance is rapidly lowered so that the breakdown voltage is reduced. As a result, the LED is bypassed to prevent application to the device.

The PTC 300 refers to a device in which the resistance changes nonlinearly according to an internal temperature. In the present embodiment, a polyswitch, which is a polymer PTC, is used.

Polyswitch is composed of special polymer and conductive material, so it is composed of chain having low electrical resistance in the state of steady bonding of conductive material in crystal structure. At this time, the Joule heat due to the current through the polyswitch is insignificant and there is no change in the crystal structure. However, when Joule heat is generated in proportion to the square of the current strength due to the overcurrent, the crystal structure is changed to an amorphous polymer structure, and the internal electrical resistance is rapidly increased, thereby limiting the overcurrent. After the cause of the overcurrent is removed and the internal temperature decreases, an internal chain is formed again to recover the low resistance value.

Referring to Figure 3 will be described in more detail the characteristics of the poly switch.

In polyswitches, the structure of the polymer changes with temperature, and the resistance changes. That is, at the low temperature points 1 and 2, the resistance gradually increases with temperature change. This change shows a gentle curve up to three points, but from three points, the electrical resistance increases sharply to four points with a small change in temperature. From point 4, the curve is displayed again.

Applying this characteristic to the LED lighting driving circuit, when the overcurrent flows and the temperature of the polyswitch reaches three points due to Joule heat, the electrical resistance increases drastically to control the overcurrent. In addition, if the cause of the overcurrent is removed, the temperature is lowered again to return to the usual low resistance value.

This feature of the polyswitch can serve as a protection device to protect the LED circuit, but until now, some factors have to be installed in a certain range to ensure that the polyswitch clearly distinguishes the normal state from the overcurrent state. I did not know if I could do it properly. Thus, the present invention proposes a method that can present these criteria by further studying the physical properties of the polyswitch.

The equation governing the operation of the polyswitch can be described as follows according to the principles of thermodynamics, heat transfer and joule.

Where m = mass of the polyposition, Cp = heat capacity of the polyposition, ΔT = temperature change of the polyposition, Δt = time variation, I = current through the polyposition, R = resistance of the polyposition, U = heat transfer constant, T = temperature of the polyposition, T _A = ambient temperature.

 In the above equation, the left side term represents the amount of heat accumulated in the polyswitch, the first side of the left side represents the Joule's heat by the intensity of the current passing through the poly switch, and the second term represents the amount of heat escaping to the surroundings.

Here, according to FIG. 2, the temperature change between the three points and the four points, which are sections in which the electrical resistance of the polyswitch increases rapidly, is very small. That is, in this case, if ΔT ≒ 0 in [Equation 1] and the temperature at this time is the operating temperature T _O , the following equation is obtained.

In the above equation, U (T ₀ -T _A ) is almost constant, which means that V ² / R is constant.In conclusion, as the input voltage V increases at the point where the polyswitch operates, the electrical resistance R increases with the square of V.

 It means a sharp increase in proportion.

On the other hand, in the polyswitch, the hold current Ih does not operate up to this current value at a constant ambient temperature T _A , and refers to the maximum value of the normally operating current, and the trip current It from this current value. Absolute operation is the minimum current value that can be judged as overcurrent.

However, this hold current or trip current does not have a fixed value but changes depending on the ambient temperature. In other words, as the ambient temperature increases, the energy for operating the polyswitch decreases. Therefore, as shown in FIG. 4, the trip current and the hold current decrease as the ambient temperature rises.

0 ℃ 20 ℃ 40 ℃ 50 ℃ 60 ℃
RXE050 060 0.50 0.41 0.36 0.32
RXE065 0.77 0.65 0.53 0.47 0.41
RXE075 0.89 0.75 0.61 0.54 0.47

[Table 1] shows the hold current value according to the ambient temperature of the actual polyswitch model (Tyco Electronics Inc. manual).

As described above, since the values of the hold current and the trip current vary according to the ambient temperature, there are many problems in that the polyswitch operates correctly as the user intends. That is, even though overcurrent flows to cut off the current according to the change of the ambient temperature, the resistance may not be changed properly, and the overcurrent may not be blocked. Sometimes it turns off.

With reference to FIG. 5, this case will be described in more detail. 5 shows the change of the hold current according to the external temperature of the polyswitch 1 and the polyswitch 1 and the other polyswitch 2. Here, the rated current through the LED is 20mA, the maximum current is 50mA.

In the case of poly switch 1, the hold current is lower than the rated current of the LED at the maximum external temperature T _h = 60 ℃, so the current supplied to the LED is likely to be limited. Therefore, in this case, there is a possibility that the illuminance of the LED suddenly decreases or even the light goes out despite the normal state.

On the other hand, the hold current of the polyswitch No. 1 at the minimum external temperature T _L = 0 ° C is between the rated current and the maximum current. Therefore, in this case, since the hold current is lower than the hold current when the rated current flows, the polyswitch maintains a low resistance state and the LED emits light normally. In addition, when a current larger than the maximum current flows, a current larger than the hold current of the poly switch 1 flows, thereby increasing the resistance of the poly switch 1 to limit the current.

In conclusion, polyswitch No. 1 is likely to malfunction near the highest external temperature.

In case of polyswitch 2, the hold current of polyswitch 2 is between rated current and maximum current at the maximum external temperature T _h = 60 ℃. Therefore, in this case, since the hold current is lower than the hold current when the rated current flows, the polyswitch maintains a low resistance state and the LED emits light normally. In addition, when a current greater than the maximum current flows, a current larger than the hold current of the second poly switch flows, thereby limiting the current by increasing the resistance of the first poly switch.

On the other hand, since the hold current is higher than the maximum current of the LED at the minimum external temperature T _L = 0 ° C, the polyswitch No. 2 maintains a low resistance even if the overcurrent exceeds the maximum current. Therefore, even if the overcurrent flows to the LED, the circuit protection function is not properly performed.

In conclusion, polyswitch 2 does not fuse properly near the lowest external temperature.

As such, the ambient temperature is a very sensitive factor in the function of the polyswitch element, and the minimum external temperature and the maximum external temperature must be considered in order to properly perform the recoverable fuse role. That is, as shown in Figure 6, the hold current of the poly switch is preferably located between the rated current and the maximum current of the LED at the lowest external temperature and the highest external temperature. Since the sign of the slope does not change in the hold current graph according to the external temperature, the range of the hold current in the middle can be known when the range of the hold current at the minimum external temperature and the maximum external temperature is determined.

In this case, since the hold current is greater than the rated current of the LED at the minimum external temperature and the maximum external temperature, the LED emits light normally at the rated current. In addition, since the hold current is smaller than the maximum current of the LED in the above range, the possibility of the polyswitch limiting the current above the maximum current becomes very high.

It is preferable to install the polyswitch to satisfy the above conditions, but in actual conditions, it is not easy to find the polyswitch that satisfies the above conditions at the lowest external temperature and the highest external temperature. There is a problem that can be very high.

In order to solve this problem, the following embodiment will be described with reference to FIG. 7 a configuration of a recoverable fuse unit that can stably perform performance between the lowest external temperature and the highest external temperature using the two polyswitches shown in FIG. 5. do.

The configuration of the rectifier circuit 200 for converting to DC by receiving AC power is the same as in the previous embodiment. However, the recoverable fuse 700 is composed of two polyswitches 710 and 720 and a Negative Temperature Coefficient Thermistor 730.

The first polyposition 710 of the two polyswitches is a polyswitch having the characteristics of the lower graph in FIG. 4, and the second polyposition position 720 is a polyswitch having the characteristics of the upper graph in FIG. 4.

The NTC thermistor 730 refers to a material whose electrical resistance decreases as the temperature increases. Mix 2 or more types of metal oxides such as Co, Mn, Ni, Cu, Fe, CuO to improve sinterability, F ₂ 0 ₃ or Li ₂ O to decrease resistance, Cr ₂ O to increase resistance It is a sintered body calcined at high temperature of 1200 ~ 1400 ℃ and has stable spinel structure or rock salt structure, so resistance has negative temperature coefficient.

The recoverable fuse 700 includes the second polyposition 720 and an NC thermistor 730 connected in series, and has a first poly with respect to the second polyposition 720 and the NC thermistor 730. Positions 710 are connected in parallel. As for the NTC thermistor 730, it is more preferable to use a critical temperature resistor (CTR) whose electrical resistance changes rapidly between the lowest external temperature and the highest external temperature.

Referring to the operation of the recoverable fuse 700, the NTC thermistor 730 has a very high electrical resistance than the first polyposition at the lowest external temperature, the current is mostly through the first polyposition 710. Is sent. In addition, when the rated current flows at the highest external temperature, the first pole position 710 becomes more than the hold current, and thus, the resistance increases rapidly due to a tripping state. At the highest external temperature, the resistance of the NC thermistor 730 is lowered and the hold current of the second polypolish 720 is higher than the rated current of the LED so that the current flows through the second polypolist 720.

In this manner, the current flows through the first polyposition 710 near the lowest external temperature, and the current flows through the second polyposition 730 near the highest external temperature.

Therefore, the problem mentioned above through the configuration as in the present embodiment, that is, the second pole position 720 at the minimum external temperature does not operate above the maximum current of the LED, the first pole position 710 at the highest external temperature ) Can solve the problem that the resistance value increases even though the rated current flows.

The resistor 400 is for voltage distribution with the LED unit 600 and is connected in series with the LED unit 600.

The constant current device 500 is a diode capable of supplying a constant current even when there is a voltage fluctuation and may allow a stable current to flow in the LED unit 600.

In the LED unit 600, eight LEDs having a forward drop voltage of about 2V are connected in series. In addition, the LED unit 600 is again connected to the second node 220 of the bridge rectifier circuit.

Through such a basic configuration, it is possible to provide an LED driving circuit directly connected to an AC power source without a separate LED converter, and can obtain a sense of reliability that can operate very stably according to the use environment.

100: control unit 110: power supply unit
120: LED driver 200: rectifier circuit
300: poly switch 400: resistance
500: constant current device 600: LED
700: recoverable fuse 730: NC thermistor

Claims (6)

A rectifier circuit for receiving an AC voltage and rectifying it with a DC;
LED for emitting light by receiving the output of the rectifier circuit; And
And a recoverable fuse for blocking an overcurrent flowing to the LED between the rectifier circuit and the LED,
And the recoverable fuse unit includes a second PTC and a (-) temperature coefficient thermistor connected in series, and a first PTC is connected in parallel with the second PTC and the (-) temperature coefficient thermistor. The method of claim 1,
When the normal input current is In and the maximum allowable current is Im,
At a preset maximum ambient temperature, the hold current Ih2 of the second PTC is In <Ih2 <Im,
LED holding device, characterized in that the hold current Ih1 of the first PTC at a predetermined minimum ambient temperature is In <Ih1 <Im. The method of claim 2,
At a preset maximum ambient temperature, the hold current Ih1 of the first PTC is Ih1 <In
LED lighting drive, characterized in that the hold current Ih2 of the second PTC at the predetermined minimum ambient temperature is Ih2> Im. The method according to claim 2 or 3,
The (-) temperature coefficient thermistor is a LED lighting drive, characterized in that the electrical resistance is rapidly lowered between the predetermined maximum ambient temperature and the minimum ambient temperature (CTR). delete delete

Images