KR100943966B1 - Apparatus for controlling LED lamp to prevent overheat, and method for the same - Google Patents

Abstract

By controlling the LED lamps in a constant current method, power consumption of the constant current LED driver can be reduced, and when the heat generation temperature of the LED lamps increases, the drive current is automatically limited to prevent overheating of the LED lamps. A constant current type light emitting diode lighting control device and method are provided. A constant current type LED lamp control method for preventing overheating includes: a) generating a first pulse width modulation (PWM) signal according to a control signal for turning on the LED lamp; b) driving the LED lamp in a constant current manner according to the first PWM signal and outputting illumination light; c) measuring the temperature of said LED lamp and comparing it with a reference temperature; d) generating a second PWM signal whose duty ratio is adjusted when a temperature of the constant current driven LED lamp is greater than a reference temperature; And e) driving the LED lamp in a constant current manner according to the second PWM signal to output the illumination light.

LED, lighting, temperature sensor, constant current drive, overheating, pulse width modulation

Description

Light emitting diode lamp control device and method for preventing overheating {Apparatus for controlling LED lamp to prevent overheat, and method for the same}

1A to 1C are diagrams illustrating a light emitting diode driving apparatus of a general constant voltage method and a constant current method, respectively.

2 is a block diagram of a light emitting diode lamp control apparatus of the constant current type for preventing overheating according to an embodiment of the present invention.

3 is a configuration diagram of the constant current LED driver of FIG. 2.

4 is a circuit diagram of the constant current LED driver of FIG. 2.

5A and 5B are diagrams illustrating PWM signal generation when light emitting diodes according to an exemplary embodiment of the present invention are below and above a reference temperature, respectively.

6 is a view illustrating an operation waveform of the constant current LED driver according to an embodiment of the present invention.

7 is a flowchart illustrating a method of controlling a LED lamp of a constant current type to prevent overheating according to an exemplary embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

100: signal processor 200: LED and temperature sensor

110: microcontroller 120: PWM signal generator

130: analog / digital converter 210: constant current LED driver

220: light emitting diode (LED) 230: temperature sensor

The present invention relates to a light emitting diode lighting control device and a method thereof, and more particularly, to a light emitting diode (LED) lighting device, a constant current type LED lighting control device for preventing overheating and a method thereof.

LED lighting is recognized as a next-generation light source because it is excellent in energy saving effect and can be used semi-permanently compared to other light sources. In addition, recently, the problem of low luminance of LEDs used in LED lightings has been greatly improved, and the application market using LEDs has spread to the entire industry, thus foreseen a full-scale LED era.

These LEDs are driven by current control or voltage control.

1A to 1C are diagrams illustrating a light emitting diode driving apparatus of a general constant voltage method and a constant current method, respectively.

FIG. 1A illustrates current limiting by connecting LED 12 and resistor 13 in series to the output of constant voltage power supply 11.

Fig. 1B shows a constant voltage type LED driving device, in which the switch element 14 is inserted in series with the LED 12 and turned on / off at a predetermined timing. In other words, in order to stably adjust the brightness over a wide dynamic range, the current flowing through the LED is turned on / off at a constant timing, and the brightness is adjusted by the ratio of the on / off period.

However, in the LED driving apparatus of the constant voltage type, the brightness of the LED changes when the voltage is changed, and there is a concern that the circuit may be damaged when an overload occurs. In addition, in the 24V constant voltage circuit, it consumes about 21.6W, which consumes 13.5W in the driver, compared to 8.1W in the LED. The power consumption in these driving circuits is all converted to heat, so that approximately 63% of power consumption is consumed as heat in the circuit.

1C illustrates a method of using a constant current power supply 15 as a light emitting diode driving apparatus of a constant current method. In such a drive device, the brightness of the LED 12 can be adjusted by reducing the current value. The change of the current value indicates that the resistor 16 is inserted in series with the LED 12, the current value is detected by the potential difference between both ends thereof, and the feedback control is performed to control the current value to the target value.

On the other hand, as described above, in the case of the constant voltage driving circuit, the LED lamps consume substantially more power than the power consumption of the LEDs.

According to the prior art, the LED lamp is converted to heat, the power consumed for driving in addition to the LED rating, most of the heat, which causes the LED to not give the brightness of the rating, due to the continuous increase in temperature, as well as the brightness of the LED There is a problem that the life is reduced.

In addition, even when trying to detect the heat generated from the LED is detected along with the heat generated from the driving circuit, there is a problem that it is difficult to perform accurate LED heat detection and power control that causes the LED degradation.

Some embodiments of the present invention for solving the above problems, while preventing overheating of the LED, by controlling the power supply by detecting the correct amount of heat of the LED lamp, the device and method for extending the LED life and prevent the malfunction of the power control To provide.

In addition, the present invention provides a device and method that can prevent the LED overheating while reducing unnecessary power consumption and heat generation in the circuit as much as possible.

In order to achieve the above technical problem of the present invention, the LED lamp control apparatus according to the first aspect of the present invention, the constant current LED driver for driving the LED lamp in a constant current method in response to the input of the PWM signal; An LED lamp driven by the constant current LED driver to output illumination light; A temperature sensor measuring a temperature of the LED lamp; An analog / digital converting unit converting the analog value measured by the temperature sensor into a digital value; A pulse width modulation signal generator for generating the PWM signal for controlling the constant current driving of the LED lamp in response to the measured digital value; And controlling a duty ratio of a pulse width modulation (PWM) signal according to a control signal for turning on the LED lamp, and corresponding to the temperature measured by the LED lamp. It includes a microcontroller to control the duty ratio of. Here, the temperature sensor accurately measures only the temperature of the LED lamp in conjunction with the constant current LED driver.

In addition, when the temperature of the LED lamp increases, the constant current LED driver reduces and drives the current flowing through the LED lamp in response to the PWM signal with the duty ratio adjusted.

In addition, the LED lamp control method according to the second aspect of the present invention, a) generating a first pulse width modulation (PWM) signal in accordance with a control signal for turning on (LED) the LED lamp; b) driving the LED lamp in a constant current manner according to the first PWM signal and outputting illumination light; c) measuring the temperature of said LED lamp and comparing it with a reference temperature; d) generating a second PWM signal whose duty ratio is adjusted when a temperature of the constant current driven LED lamp is greater than a reference temperature; And e) driving the LED lamp in a constant current manner according to the second PWM signal to output the illumination light.

Here, step d) may include d-1) converting the measured temperature into a digital value; d-2) comparing the measured temperature converted into the digital value with a reference temperature; And d-3) adjusting the duty ratio of the first PWM signal according to the comparison result.

In addition, a plurality of reference temperatures exist, and the second PWM signal having a different duty ratio may be generated depending on whether the reference temperature is exceeded.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

As an embodiment of the present invention, a constant current circuit with low power consumption is used to effectively drive a lighting LED, and a temperature sensor is adopted to prevent the LED from being damaged due to abnormal overheating, so that the LED temperature does not rise above a certain temperature. Provided are a constant current type LED lighting control device for controlling overheating and a method thereof.

Light emitting diode lamp control device of the constant current method for preventing overheating according to an embodiment of the present invention, it is possible to automatically adjust the current supplied to the circuit in accordance with the change in the input voltage, for example, at an input voltage of 12 ~ 30V In the constant current circuit in operation, power consumption of 8.1 W is consumed in the LED and only 1.5 W is consumed in the LED driver, so that there is almost no heat generation in the driver other than the LED self-heating.

First, Figure 2 is a block diagram of a light emitting diode lamp control device of the constant current method for preventing overheating according to an embodiment of the present invention.

Referring to FIG. 2, the LED controller for controlling a constant current type for preventing overheating according to an exemplary embodiment of the present invention includes a signal processing unit 100, an LED, and a temperature sensing unit 200, and the signal processing unit 100. ) Includes a microcontroller (MCU) 110, a PWM signal generator 120, and an analog / digital (A / D) converter 130, and the LED and the temperature detector 200 include a constant current LED driver 210. It may include an LED lamp 220 and a temperature sensor 230.

The microcontroller 110 receives a control signal for turning on the LED lamp 220, and the duty ratio of the pulse width modulation (PWM) signal is controlled according to the control signal. In addition, the duty ratio of the PWM signal is controlled in response to the temperature measured from the LED lamp 220.

The pulse width modulation signal generator 120 generates the PWM signal for controlling the constant current driving of the LED lamp 220 under the control of the microcontroller 110.

The constant current LED driver 210 drives the LED lamp 220 in a constant current manner in response to the PWM signal. Constant current LED driver 210 according to an embodiment of the present invention when the temperature of the LED lamp 220 rises, driving by reducing the current flowing in the LED lamp 220 in response to the PWM signal of the duty ratio is adjusted Done.

The LED lamp 220 is driven by the constant current LED driver 210 to output the illumination light.

The temperature sensor 230 measures the temperature of the LED lamp 220. In the conductor, the electrical resistance changes as the temperature changes. Using this characteristic, if the resistance change rate for the unit temperature change is known, the corresponding temperature can be measured only by the resistance value, which is called a temperature sensor. Here, the resistance variation rate with respect to the unit temperature is called a temperature coefficient, and when the resistance value increases at the temperature increase, the positive temperature coefficient is called a negative temperature coefficient when the resistance value decreases. The temperature sensor according to the embodiment of the present invention may be an integrated circuit (IC) temperature sensor, the IC sensor is used to change the current voltage characteristics of the PN junction according to the temperature, there is a voltage output type and current output type, the constant current It may be embedded in the LED driver 210.

The analog / digital converter 130 converts the analog value measured by the temperature sensor 230 into a digital value. The analog / digital converting unit 130 according to the embodiment of the present invention may be embedded in the microcontroller 110. The converted digital value may be an analog temperature value. In addition, the converted digital value may be a digital value for the comparison result if the temperature sensor is compared with the reference temperature and the LED heating temperature. If a plurality of reference temperatures are set, the digital values may also be plural. Alternatively, if the converted digital value may be a difference between the reference temperature and the LED temperature, the duty ratio of the PWM signal may be adjusted to the plurality of difference values.

In an embodiment of the present invention, the microcontroller 110 compares the measured temperature converted into a digital value in the analog / digital converter 130 and a preset reference temperature, and the duty ratio of the PWM signal according to the comparison result. Will be controlled. As a result, when the measured temperature is greater than the reference temperature, the microcontroller 110 reduces the duty ratio of the PWM signal to a value less than 1, and when the measured temperature is smaller than the reference temperature, The duty ratio is kept at 1.

As a result, the constant current LED driving circuit 210 according to the embodiment of the present invention is designed to flow a predetermined constant current (for example, LED rated current) when the duty ratio is 1, and is proportional to the value set according to the duty ratio. Constant current flows. Therefore, when the measured temperature in the microcontroller 110 is greater than the reference value compared to the reference temperature, it is possible to prevent overheating in the LED lamp by reducing the duty ratio of the PWM signal.

Note that in the above-described embodiment of the present invention, the constant current LED driving circuit and the temperature sensor are mutually coupled to perform more accurate control according to the heat generation amount of the LED. That is, the constant current circuit consumes very low power in the circuit in the constant voltage circuit.

For example, if a constant voltage circuit consumes 8.1 W of LED at a 24 V input voltage, 13.5 W is consumed in the circuit, which is released as heat. However, if the constant current circuit consumes 8.1W of LED at 12 ~ 30V input voltage, the power consumed by the circuit is only 1.5W. Therefore, by adopting a constant current circuit and a temperature sensor together in the embodiment of the present invention, not only unnecessary power consumption can be lowered, but also more accurate heat generation of the LED can be sensed. If the conventional technology and the constant voltage circuit are adopted, the heat emitted from the driving circuit is misrecognized as heat generation of the LED, thereby unnecessarily lowering the LED brightness.

However, according to the embodiment of the present invention, since the heat generation in the circuit other than the LED self-heating is considerably low, more accurate heat generation can be detected, and the life of the LED can be extended based on the heat generation detection.

3 is a configuration diagram of the constant current LED driver of FIG. 2.

Referring to FIG. 3, the constant current LED driver according to an embodiment of the present invention may be implemented in an integrated circuit form, and the constant current LED driver IC 210 may include an input voltage terminal Vin, a sense current terminal, A drain output terminal LX, an on / off terminal ADJ, and a ground voltage terminal GND of the switching transistor may be included. The constant current LED driver according to the embodiment of the present invention shows a portion excluding the LED 220, but for convenience, the same reference numeral 210 as the constant current LED driver IC will be used.

For example, the input voltage Vin of the constant current LED driving IC 210 is 12 to 30 V, and a current sensing resistor Rs is connected between the input voltage Vin and one terminal of the coil L1. The LED 220 may be connected between the other terminal of the coil L1 and the drain output terminal LX of the constant current LED driving IC 210.

In addition, a Schottky diode D1 may be connected between the input voltage Vin and the anode of the LED 220, and a capacitor C1 may be connected between the input voltage Vin and the ground voltage terminal GND. have. This connection is for example only, but not limited to.

The constant current LED driver according to the embodiment of the present invention having the above-described configuration drives the LED 220 in a constant current manner according to a PWM signal input through the on / off terminal ADJ.

4 is a circuit diagram of the constant current LED driver of FIG. 2.

4, a constant current LED driving IC 210 according to an embodiment of the present invention includes a voltage regulator 211, a shutdown circuit 212, a current sensing circuit, a comparator, a low pass filter 213, and a switching transistor ( Q3) and the like.

The input DC power supply Vin supplies the operating power of the LED driving IC 210 to the DC voltage.

The voltage regulator 211 serves to supply a 12 to 30V input voltage by changing the voltage supplied inside the constant current LED driving IC 210 to DC 5V, and the low pass filter 213 has a cutoff frequency of 4KHz. Filter the PWM signal input through the on / off terminal (ADJ). Here, the on / off terminal ADJ receives a DC voltage or a PWM signal as an input, and the PWM signal is filtered through the low pass filter 213 according to the cutoff frequency.

The output of the low pass filter 213 drives the shutdown circuit 212. When the voltage input to the constant current LED driver IC 210 drops below 0.2V, for example, the voltage regulator 211 and the output switch are turned off. At this time, the reference voltage Vref maintains the power supply during the shutdown to supply the bias current for the shutdown circuit 212.

Here, as shown by reference numeral A, when a PWM signal is input through the on / off terminal ADJ, it is compared with the detection current through the comparator Amp2, and then the drain terminal LX of the output transistor Q3. Through the supply to the anode of the LED (220).

In the constant current LED driver IC 210 according to the embodiment of the present invention, the sense resistor Rs is a resistor having a small resistance value for generating a sense voltage generated by a forward current flowing through the LED 220.

The comparator Amp2 compares the amount of forward current If flowing through the LED 220 changed into the sense voltage by the sense resistor Rs with the reference voltage Vref, and then amplifies the difference to thereby transistor Q3. By controlling the amount of current flowing through the base of), the amount of forward current If flowing through the LED 220 is constant.

5A and 5B are diagrams illustrating PWM signal generation when the light emitting diodes according to the exemplary embodiment of the present invention are lower than or equal to a reference temperature, respectively.

5A illustrates a PWM signal in which the duty ratio is maintained when the measurement temperature of the LED lamp is lower than the reference temperature.

5B illustrates a PWM signal having a reduced duty ratio when the measured temperature of the LED lamp is greater than or equal to the reference temperature. Thus, the temperature of the LED lamp can be lowered by lowering the duty ratio of the PWM signal.

6 is a diagram illustrating an operation waveform of the constant current LED driver according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the constant current LED driver 210 according to an exemplary embodiment of the present invention may output a voltage, a sense voltage, a coil current, a comparator input voltage, and a comparator output of the drain output terminal LX as described in FIG. 4. It is a figure which shows each.

That is, when a PWM signal is input through the on / off terminal ADJ, it is compared with the detection current corresponding to the sensed voltage through the comparator Amp2, and then the LED is connected through the drain terminal LX of the output transistor Q3. A PWM signal is supplied to the anode of 220.

On the other hand, Figure 7 is a flowchart illustrating a method of controlling a LED lamp of a constant current type to prevent overheating according to an embodiment of the present invention.

Referring to FIG. 7, in the method of controlling a constant current light emitting diode lamp for overheating according to an embodiment of the present invention, first, when a control signal for turning on an LED lamp is input (S710), a pulse is controlled under the control of a microcontroller. A width modulation (PWM) signal is generated (S720). If the LED is not in the overheat state, the microcontroller maintains the duty ratio of the pulse width modulation PWM in accordance with the control signal.

Next, the LED light is driven in a constant current manner according to the PWM signal to output illumination light (S730). As described above, when the LED is driven in the constant current method, power consumption and heat generation are hardly generated in the circuit.

Next, the analog temperature of the LED lamp is measured (S740), and the analog temperature is converted into a digital value (S750).

Next, the measured temperature is compared with a predetermined reference temperature, for example, greater than 80 (S760), and according to the comparison result, the duty ratio of the PWM signal is adjusted (S770). Here, if the measured temperature is greater than the reference temperature, the duty ratio of the PWM signal is reduced to a value less than 1, and if the measured temperature is less than the reference temperature, the duty ratio of the PWM signal is maintained at 1 Can be.

Next, the LED light is driven in a constant current manner according to the PWM signal whose duty ratio is adjusted to output the illumination light (S780).

As a result, according to an embodiment of the present invention, by controlling the LED lamp in a constant current method, and by adjusting the duty ratio of the PWM signal applied to the LED lamp driving circuit can limit the drive current automatically when the temperature rise of the LED lamp Will be.

In the embodiment shown in Figure 7 is described as converting the analog LED temperature to the digital LED temperature and then compared with the reference temperature, the configuration that compares the analog temperature itself with the reference temperature is also within the spirit of the present invention will be apparent to those skilled in the art. Will understand.

In addition, the reference temperature compared with the LED temperature may be plural, and the configuration in which the duty ratio of PWM is adjusted according to each reference temperature will also be included in the spirit of the present invention.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

According to the present invention, by controlling the light emitting diode (LED) lamp in a constant current method, it is possible to reduce the power consumption of the constant current LED driver, and when the heating temperature of the LED lamp rises, by automatically limiting the driving current, Overheating can be prevented.

In addition, by minimizing heat generated in the driving circuit and accurately detecting only the heating temperature of the LED lamp, it is possible to perform optimal control to prevent deterioration of the LED lamp without unnecessary brightness change.

Claims (12)

In the constant current type light emitting diode (LED) lighting lamp control device, In response to the input of the PWM signal, the LED lamp is driven in a constant current manner, and the amount of forward current flowing through the LED lamp is sensed by a sense voltage generated by the flow of the forward current through the LED lamp, and based on the detected sense voltage. A constant current LED driver for making a constant amount of forward current flowing in the LED compared to a voltage; An LED lamp driven by the constant current LED driver to output illumination light; A temperature sensor for measuring a temperature of the LED lamp based on the radiant heat emitted from the LED lamp; And An analog / digital converting unit converting the analog value measured by the temperature sensor into a digital value; A pulse width modulation signal generator for generating the PWM signal for controlling the constant current driving of the LED lamp in response to the measured digital value; And A microcontroller controlling a duty ratio of the PWM signal according to a control signal for turning on the LED lamp and controlling the duty ratio of the PWM signal in response to a temperature measured by the LED lamp; Include, The temperature sensor is connected to the constant current LED driving unit, LED lamp control device that can detect the heating of the lamp excluding the heating of the circuit. The method of claim 1, The constant current LED driving unit, when the temperature of the LED lamp rises, LED lamp control device characterized in that for driving by reducing the current flowing in the LED lamp in response to the PWM signal of the duty ratio is adjusted. The method of claim 1, The micro controller compares the measured temperature converted into a digital value by the analog / digital converter and a preset reference temperature, and controls the duty ratio of the PWM signal according to the comparison result. The method of claim 3, And the microcontroller reduces the duty ratio of the PWM signal to a value less than 1 when the measured temperature is greater than the reference temperature. The method of claim 3, And the microcontroller maintains the duty ratio of the PWM signal at 1 when the measured temperature is less than the reference temperature. The method of claim 3, The reference temperature is set a plurality, LED lighting control device for generating a PWM signal of a different duty ratio in accordance with the comparison value of the reference temperature. The method of claim 1, The temperature sensor is an LED lamp, characterized in that the integrated circuit (IC) temperature sensor embedded in the constant current LED driver. In the constant current type light emitting diode (LED) lamp control method, a) generating a first pulse width modulation (PWM) signal according to a control signal for turning on the LED lamp; b) driving the LED lamp in a constant current manner according to the first PWM signal, and detecting a sense voltage generated by the flow of a forward current through the LED lamp by the amount of forward current flowing through the LED lamp, and the sensed voltage sensed Comparing the reference voltage with a reference voltage and outputting illumination light by making the amount of forward current flowing through the LED constant; c) measuring the temperature of the LED lamp excluding circuit heating based on the radiant heat emitted from the LED lamp and comparing it with a reference temperature; d) generating a second PWM signal by adjusting a duty ratio of the first PWM signal when the temperature of the constant current driven LED lamp is greater than a reference temperature; And e) outputting the illumination light by driving the LED lamp in a constant current manner according to the second PWM signal; LED lighting control method comprising a. The method of claim 8, wherein the d) step, d-1) converting the measured temperature into a digital value; d-2) comparing the measured temperature converted into the digital value with a reference temperature; And d-3) adjusting the duty ratio of the first PWM signal according to the comparison result LED lighting control method comprising a. The method of claim 9, The reference temperature of step d-2) is the LED lamp control method, characterized in that 80 degrees Celsius. The method of claim 9, And controlling the duty ratio of the first PWM signal to a second PWM signal of less than one when the measured temperature is greater than the reference temperature in step d-3). The method of claim 8, wherein the reference temperature is provided in plural, and generates a second PWM signal having a different duty ratio depending on whether the reference temperature is exceeded.

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