JP5472691B2 - LED lighting device and lighting apparatus - Google Patents

Description

  The present invention relates to an LED lighting device that lights a light emitting diode and a lighting fixture including the same.

  An LED lighting device that lights an LED using a DC converter provided with a switching element is known (see, for example, Patent Document 1). The LED lighting device described in Patent Document 1 boosts an alternating rectified voltage with a boost chopper and smoothes it to supply a plurality of series circuits composed of a plurality of light-emitting diodes to an LED lamp connected in parallel. The boost chopper is controlled by a control circuit so that it can be dimmed and the power factor can be improved.

  Depending on the number of LED lamps in series and the power supply voltage used, the LED lamps can be turned on using an LED lamp lighting circuit mainly composed of a step-down chopper, or a combination of a step-up chopper and a step-down chopper connected in cascade. May be.

  When an LED is lit using a DC converter, the output of the DC converter is generally constant so that the LED of the load is not affected by fluctuations in the input power supply and the load. Moreover, in order to supply a stable output against minute fluctuations in the input power supply and the load, an appropriate delay is given to the feedback control. For example, when the input power supply voltage is lowered, the ON period of the switching element of the DC converter is extended after an appropriate time delay to compensate for the decrease in output current accompanying the voltage drop.

Japanese Patent Application Laid-Open No. 11-066771

  However, in the prior art, if the ON period of the switching element of the DC converter is extended due to the time delay of the feedback control when the fluctuation is restored, an excessive peak current flows into the DC converter and the LED. become. As a result, when the peak current exceeds the pulse current rating of the LED, there is a problem that the life of the LED is shortened or destroyed.

  An object of the present invention is to provide an LED lighting device in which a peak value of an output current does not exceed a pulse current rating of an LED when a change in at least one of an input power supply and a load is restored, and a lighting fixture including the LED lighting device. To do.

In order to solve the above-described problems, an LED lighting device of the present invention includes a DC conversion device that includes at least one switching element and lights an LED by an output current; and the DC voltage that the input voltage of the DC conversion device fluctuates. an output current detecting means for detecting by the output current of the converter; based on the detection output of the output current detecting means, when the input voltage of the DC converter is detected to be lowered, the DC converter the output current, along with increased by increasing the duty of the switching drive signal of the switching element with a time lag, when the fluctuation of the input voltage has returned, the output current of the DC converter, the switching by reducing narrows the duty of the switching drive signal for the device, the peak value of said output current It is characterized in that it comprises a; suppress and control means so as not to exceed the LED pulse current rating.

In the present invention, the control means reduces the output current of the DC converter when the fluctuation of at least one of the input voltage and the load is restored by reducing the duty of the switching drive signal of the switching element . since the peak value of the output current may be suppressed so as not to exceed the pulse current rating of LED, the remaining concrete means are not particular limited. For example, the following aspects can be adopted.

The first aspect, the control means, said switching element is OFF of the DC converter when the load of the LED is restored, the pulse current rating peak value of the LED of the output current of the DC converter To avoid exceeding.

Second aspect, the control means limits the predetermined period feedback control range when the load of the LED is varied, so that the peak value of the output current of the DC converter does not exceed the pulse current rating of the LED To suppress.

  According to a third aspect, the control means reduces the reference voltage of the feedback circuit for a predetermined period when at least one of the input voltage and the load fluctuates, and when the fluctuation is restored, the peak value of the output current of the DC converter Is controlled so as not to exceed the pulse current rating of the LED.

  The lighting fixture of this invention has comprised the lighting fixture main body and the LED lighting device. The luminaire may be provided with an LED as a light source, and its use is generally for illumination purposes, but is not limited thereto. The luminaire main body refers to all remaining portions from which the LED and the LED lighting device are removed from the luminaire. The LED lighting device is the LED lighting device of the present invention described above.

The present invention detects that the input voltage fluctuates from the output current of the DC converter that turns on the LED, and increases the duty of the switching element of the DC converter with a time delay when the power supply voltage decreases. In this way, the output current of the DC converter is increased to compensate for the influence of fluctuation, and when the fluctuation is restored, the output current of the DC converter is reduced by reducing the duty of the switching drive signal of the switching element, By providing a control means that suppresses the peak value of the output current of the DC converter so as not to exceed the pulse current rating of the LED, a current exceeding the pulse current rating flows to the LED when the above fluctuation is restored. Therefore, it is possible to provide an LED lighting device that prevents shortening or destroying the life of the LED and a lighting fixture equipped with the LED lighting device. It achieves the effect that.

It is a circuit diagram concerning the 1st form for carrying out the present invention. It is a waveform diagram of the input power supply voltage and the output current of the DC converter similarly. It is a wave form diagram of a drive signal of a switching element of a direct-current converter similarly corresponding to each state of input power supply voltage. It is a circuit diagram concerning the 2nd form for carrying out the present invention. It is a waveform diagram of the input power supply voltage and the output current of the DC converter similarly. It is a wave form diagram of a drive signal of a switching element of a direct-current converter similarly corresponding to each state of input power supply voltage. It is a circuit diagram concerning the 3rd form for carrying out the present invention. It is a waveform diagram of the input power supply voltage and the output current of the DC converter similarly.

  Hereinafter, embodiments of the present invention will be described in detail.

The first embodiment of the present invention has a circuit configuration as shown in FIG. That is, the LED lighting device includes a DC converter 1, an output current detector 2 and a controller 3 as essential circuit means, and an LED 4 as a load is connected to the output terminal of the DC converter 1. Further , a rectified DC power source 5 is provided on the input side of the DC converter 1 as an auxiliary circuit means.

In this embodiment, the DC converter 1 includes a step-up chopper 11 and a step-down chopper 12. The choppers 11 and 12 are connected in cascade between a rectified DC power source 5 and a load LED 4 to be described later, thereby forming the DC converter 1.

  The step-up chopper 11 includes a series circuit of an inductor L1 and a switching element Q1 connected to a DC output terminal of a rectified DC power supply 5 described later, and a series circuit of a flywheel diode D1 and a smoothing capacitor C1 connected in parallel to the switching element Q1. Thus, the boosting operation and the power factor correction operation are performed under the control of the control means 3 described later. Note that the switching element Q1 is formed of a MOSFET as an example.

  The step-down chopper 12 includes a switching element Q2 as a current control element connected between both ends of a smoothing capacitor C1 that is an output end of the step-up chopper 11, and a series circuit of a flywheel diode D2, an inductor L2 connected in parallel to the flywheel diode D2, and A series circuit of a capacitor C2 is provided, and a step-down operation is performed under the control of the control means 3 described later, and a desired DC current is output to the LED 4. The switching element Q2 is made of a MOSFET as an example.

  The output current detection means 2 includes a resistor R1 as a current detection element inserted in series between the flywheel diode D2 and the capacitor C2. The output current of the DC converter 1 is detected using the voltage drop of the resistor R1, and the output of the output current is controlled and input to the control means 3.

  The control means 3 is means for performing the following control by supplying the drive signal that is controlled as required to the step-up chopper 11 and the step-down chopper 12 mainly to the switching elements Q1 and Q2. That is, when the output of the DC converter 1 is made constant by feedback control with a time delay based on the detection output of the output current detection means 2, and when at least one of the input voltage and the load of the LED 4 fluctuates and returns, The peak value of the output current from the DC converter 1 is suppressed so as not to exceed the pulse current rating of the LED 4.

  In this embodiment, the control means 3 includes a first voltage comparator 31, first and second drive signal generation circuits 32 and 33, a second voltage comparator 34, and an OFF control circuit 35, and an input voltage When the fluctuation of at least one of the loads of the LED 4 is restored, the switching element Q2 of the DC converter 1 is turned off to suppress the peak value of the output current of the DC converter 1 from exceeding the pulse current rating of the LED 4. To do.

  The first voltage comparator 31 is mainly composed of an operational amplifier 31a, and the output terminal of the output current detection means 2 is connected to the non-inverting input terminal of the operational amplifier 31a. Further, the first reference voltage source E1 is connected to the inverting input terminal to provide a reference voltage for comparison to the first voltage comparator 31. The first reference voltage source E1 applies a reference voltage necessary for sensing the occurrence of voltage fluctuation to the inverting input terminal of the operational amplifier 31a. Therefore, the first voltage comparator 31 detects a change in the AC voltage and controls a second drive signal generation circuit 33 described later.

  Further, a capacitor C3 is connected between the output terminal of the operational amplifier 31a and the inverting input terminal to give an appropriate time delay to the feedback control. Then, the feedback signal obtained from the output terminal of the operational amplifier 31a is input to the second drive signal generation circuit 33, and a controlled drive signal is generated for the switching element Q2 of the step-down chopper 12 to generate a DC conversion. Negative feedback control is performed on the output current of the device 1.

  The first drive signal generation circuit 32 generates a drive signal to be supplied to the switching element Q1 of the boost chopper 11. The first drive signal generation circuit 32 can be configured by using a function built in the unitized boost chopper device. However, if desired, the entire control means 3 can be configured using a semiconductor device such as a microcomputer or an IC as a unitized control device.

  The second drive signal generation circuit 33 is controlled by the first voltage comparator 31 to generate a drive signal to be supplied to the switching element Q2 of the step-down chopper 12. That is, when a power supply voltage fluctuation has not occurred, a drive signal is generated with a duty in a normal state and supplied to the switching element Q2 of the step-down chopper 12 to drive it. When the first voltage comparator 31 senses a voltage drop due to power supply voltage fluctuation, the duty of the drive signal is increased with an appropriate time delay.

  The second voltage comparator 34 is mainly composed of an operational amplifier 34 a, and its non-inverting input terminal is connected to the output terminal of the output current detection means 2. The second reference voltage source E2 is connected to the inverting input terminal. The output terminal of the operational amplifier 34a controls an OFF control circuit 35 described later. Since the operational amplifier 34a is not connected to a capacitor as in the operational amplifier 31a, the operational amplifier 34a does not have a time delay characteristic, and thus reacts promptly to the output of the output current detection means 2. The second reference voltage source E2 is set to have a potential higher than that of the first reference voltage, and is set so as to sense an output current having a value less than or equal to the pulse current rating of the LED 4.

The OFF control circuit 35 operates when the second voltage comparator 34 generates an output, and prioritizes the second drive signal generation circuit 33 to switch the switching element Q2 of the step-down chopper 12 to the on-duty of the drive signal. It is turned OFF to narrow the time width. As a result, the duty of the second switching element Q2 becomes narrow, and the output current of the DC converter 1 is suppressed.

  The LED 4 acts as a load of the DC converter 1 and is connected to the output end of the DC converter 1, and hence the output end of the step-down chopper 12, for example, in a state where a plurality of the LEDs 4 are connected in series. If desired, a plurality of series circuits composed of a plurality of LEDs can be connected to the output terminal of the DC converter 1 in parallel. In this case, however, it is desirable to incorporate constant current circuits in each of the plurality of series circuits so that the load currents flowing in the respective series circuits are controlled to be equal.

  In this embodiment, the rectified DC power source 5 is composed of a bridge-type full-wave rectifier circuit whose AC input terminal is connected to the commercial AC power source 6, and outputs a non-smooth DC voltage by full-wave rectifying the AC voltage. A DC input voltage is supplied to the chopper 11.

  Next, the circuit operation in the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a waveform diagram showing the relationship between the power supply voltage fluctuation and the change in the output current associated therewith, (a) is a power supply voltage waveform diagram, and (b) is an output current waveform diagram. FIG. 3 is a drive signal waveform that is a drive signal supplied to the switching element Q2 of the DC converter 1 and whose duty changes according to the state of the output current, and (c) is a drive signal waveform in a normal state. , (D) is a drive signal waveform when the power supply is changed, and (e) is a drive signal waveform when the power supply is restored.

  First, the circuit operation of the entire LED lighting device will be described with reference to FIG. That is, the AC voltage of the commercial AC power supply 6 is full-wave rectified by the rectified DC power supply 5 and converted to a non-smooth DC voltage. This DC voltage becomes the input voltage of the step-up chopper 11. The full-wave rectified waveform is smoothed by controlling the duty ratio of the boost chopper 11 corresponding to the DC voltage waveform whose instantaneous value changes depending on the phase angle, and the boosted DC voltage is output across the smoothing capacitor C1. At the same time, the harmonic components of the input current are minimized.

  When the DC output voltage of the step-up chopper 11 is supplied as an input voltage to the input terminal of the step-down chopper 12, the step-down chopper 12 performs step-down operation, and a DC current that is made constant to match the load LED 4 is output. The LED 4 is energized and lights up.

  By the way, as shown in FIG. 2A, when the output current is I and the fluctuation f in which the AC power supply voltage decreases for a short time occurs at time t1, as shown in FIG. Further, since the output current I of the DC converter 1 decreases and becomes If, the detection output of the output current detection means 2 becomes If, and the power supply voltage fluctuation is detected. Then, the detection output from the output current detection unit 2 is input to the first and second voltage comparators 31 and 34 of the control unit 3.

  Since the potential of the non-inverting input terminal of the first voltage comparator 31 falls below the reference voltage E1 at time t2 after the time delay, the second drive signal generating circuit responds to the fluctuation f at that time. The duty of the drive signal generated from 33 is increased as shown in FIG. As a result, the on-duty of the output of the step-down chopper 12 increases at time t2, so the influence of the fluctuation f is compensated and the output current becomes I, which is the same level as in the normal state.

  The second voltage comparator 34 does not respond when the fluctuation f occurs because the reference potential of the reference potential source E2 is high.

  Next, when the fluctuation f returns to the normal state at time t3, the duty of the drive signal of the step-down chopper 12 is still large due to the influence of the time delay of the first voltage comparator 31, so that the output current of the DC converter 1 is normal. Excessive peak current flows that is larger than that in the state. The output current at this time is also detected by the output current detection means 2, and the detected output is input to the first and second voltage comparators 31 and 34 of the control means 3. Since the second voltage comparator 34 exceeds the reference voltage, an output is generated and the OFF control circuit 35 is operated. As a result, since the duty of the drive signal supplied to the step-down chopper 12 is forcibly narrowed as shown in FIG. 3 (e), the output current of the DC converter 1 is reduced as shown in FIG. 2 (b). The peak current It below the pulse current rating of the LED 4 is suppressed, and an excessive peak current It ′ exceeding the same rating indicated by a dotted line is prevented from flowing to the LED 4.

  Then, at time t3 after the time delay of the first voltage comparator 31, the second drive signal generation circuit 33 is controlled by the first voltage comparator 31 to be applied to the switching element Q2 of the step-down chopper 12. Since the duty of the drive signal to be supplied is returned to that in the normal state, the output current I of the DC converter 1 is restored, and the normal state is restored as shown in FIG. If the duration of the minute fluctuation f is shorter than the above description and is less than the time delay of the first voltage comparator 31, the output current is not compensated for the normal value I at time t2. At the time of recovery, a peak current It equal to or less than the pulse rated current of the LED 4 flows for a time delay.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to FIG. 1 thru | or FIG. 3, and the description is abbreviate | omitted. In the second embodiment, as shown in FIG. 4, the circuit configuration is such that the power supply voltage detection means 7 is disposed and the control means 3 is controlled by the power supply voltage detection means 7.

The power supply voltage detection means 7 has an input terminal connected in parallel to the AC input terminal of the rectified DC power supply 5 and controls the control means 3 by detecting a power supply voltage fluctuation.

The control means 3 narrows the duty of the drive signal generated by the second drive signal generation circuit 33 within a predetermined range when the power supply voltage detection means 7 detects the power supply voltage fluctuation.

  The circuit operation will be described with reference to FIGS. As shown in FIG. 5A, when a minute fluctuation f of the power supply voltage occurs at time t1, the power supply voltage detecting means 7 detects this and controls the second drive signal generating circuit 32. As a result, as shown in FIG. 6D, the drive signal generated from the second drive signal generation circuit 32 is such that the peak current that flows when the duty returns to the minute fluctuation f is less than the pulse current rating of the LED 4. It can be narrowed to a reasonable value. For this reason, the output current I ′ flowing at the time t2 after the time delay during the occurrence of the minute fluctuation f is lower than the current I before the minute fluctuation f is generated as shown in FIG. Since the compensation is made to such an extent that it does not have a large influence on the height, the practical influence becomes very small.

  Then, when the power supply voltage returns from the minute fluctuation f, the drive signal generated from the second drive signal generation circuit 32 during the time delay of the second voltage comparator 31 is as shown in FIG. In addition, since the duty is the same as (d), the peak current of the output current flowing at that time is suppressed below the pulse current rating of the LED 4 as indicated by It ′ in FIG. 5 (b).

Next, with reference to FIGS. 7 and 8, a description will be given of a third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 1 thru | or FIG. 3, and the description is abbreviate | omitted. In the third embodiment, the circuit configuration is the same as that of the second embodiment in that the power supply voltage detection means 7 is disposed and the control means 3 is controlled by the power supply voltage detection means 7 as shown in FIG. However, the portion of the control means 3 that responds to the power supply voltage detection means 7 is different. That is, the reference voltage source E1 of the first voltage comparator 31 is controlled to make the reference voltage variable according to the detection output from the power supply voltage detection means 7.

That is, the reference voltage of the reference voltage source E1 is controlled when the power supply voltage detecting means 7 detects the minute fluctuation f, and decreases as shown in FIG. 8 ( f ). For this reason, the drive signal of the step-down chopper 12 is narrowed to such a value that the maximum value of the duty is such that an excessive current flowing at the time of recovery is less than or equal to the pulse current rating of the LED 4.

  The circuit operation will be described with reference to FIG. As shown in FIG. 8A, when a minute fluctuation f of the power supply voltage occurs at time t1, the power supply voltage detecting means 7 detects this and lowers the reference voltage of the second drive signal generating circuit 32. As a result, the peak current that flows when the duty of the drive signal generated from the second drive signal generation circuit 32 recovers the minute fluctuation f is narrowed to a value that is less than or equal to the pulse current rating of the LED 4. For this reason, the output current It flowing at the time t2 after the time delay during the generation of the minute fluctuation f is the same as in the second embodiment, as shown in FIG. Although it is not compensated for until it is compensated to the extent that it does not significantly affect the brightness of the LED 4, the practical effect is very small.

  Then, when the power supply voltage recovers from the minute fluctuation f, since the drive signal generated from the second drive signal generation circuit 32 during the time delay of the second voltage comparator 31 has the same duty, the output current that flows The peak current is suppressed below the pulse current rating of the LED 4 as indicated by It in FIG.

DESCRIPTION OF SYMBOLS 1 ... DC converter, 2 ... Output current detection means, 3 ... Control means, 4 ... LED, 5 rectification DC power supply, 6 ... Commercial AC power supply, 7 ... Power supply voltage detection means, 11 Boost chopper, 12 ... Buck chopper, 31: First voltage comparator, 31a, 34a : Operational amplifier, 32: First drive signal generation circuit, 33: Second drive signal generation circuit, 34: Second voltage comparator, 35: OFF control circuit, C3: Capacitor, E1, E2: Reference voltage source

Claims (4)

A DC conversion device comprising at least one switching element and lighting an LED with an output current;
An output current detecting means for detecting that the input voltage of the DC converter is varied by the output current of the DC converter;
Based on the detection output of the output current detecting means, when the input voltage of the DC conversion device detects that it has decreased, the output current of the DC converter, the switching of the switching element with a time delay with increased by increasing the duty of the drive signal, when the fluctuation of the input voltage has returned, the output current of the DC converter, by reducing narrows the duty of the switching drive signal of the switching element, and suppressing control means so that the peak value of the output current does not exceed the pulse current rating of the LED;
The LED lighting device characterized by comprising. Control means, said switching element is OFF of the DC converter when the fluctuation of the load of the LED is restored, the peak value of the output current of the DC converter does not exceed the pulse current rating of the LED The LED lighting device according to claim 1, wherein the LED lighting device is suppressed as follows. Control means, characterized in that the load of the LED is limited for a predetermined period feedback control range when variation, the peak value of the output current of the DC converter can be suppressed so as not to exceed the pulse current rating of the LED The LED lighting device according to claim 1. A lighting fixture body;
LED and disposed of the luminaire body;
The LED lighting device according to any one of claims 1 to 3, wherein the LED is turned on;
The lighting fixture characterized by comprising.

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