JP6520469B2 - LED lighting device and irradiation device - Google Patents

Description

  The present invention relates to an LED lighting device and an irradiation device using the same.

  Patent Document 1 discloses a light-emitting diode luminaire for cultivating various mushrooms. The luminaire comprises a light source comprising a light emitting diode, and a PWM circuit for supplying a pulse current for blinking the light source to the light source. It is disclosed that the waveform of the pulse current is preferably one selected from the group consisting of a rectangular wave having a predetermined frequency and a predetermined on-duty, a sawtooth wave, and a chevron wave.

JP, 2009-171904, A

  As disclosed in Patent Document 1, a special purpose LED lighting device is known in which a specific pulse current is repeatedly applied to the LED, and the illuminance of the LED is increased or decreased according to the LED current. As described above, when the current of a specific waveform is applied to the LED according to the irradiation object or application of the LED lighting device, the LED current waveform is determined in consideration of each element such as the current average value, the current effective value and the current peak value. There is a need. For example, the average current value determines the amount of light substantially obtained in the object to be irradiated, the effective current value is restricted by the rated current value (life) of the LED, and the peak current value is the optical reactivity in the object to be irradiated Affect Therefore, when light is irradiated by the LED current which repeatedly increases and decreases, it is desirable that the LED current waveform be determined in consideration of the balance of each value of the current.

  Therefore, it is an object of the present invention to provide an LED lighting device capable of supplying an LED with an output current optimally determined in consideration of the balance between average value, effective value and peak value, and an irradiation device using the same. Do.

  An LED lighting device according to a first aspect of the present invention includes a DC power supply circuit that supplies an output current to the LED, a light amount detection unit that detects the light output of the LED and outputs an average value of the light output as a light amount detection value. A reference wave processing unit that generates an output reference wave of a continuous triangular wave or sawtooth wave whose amplitude is zero-peak and determines the peak value of the output reference wave so that the detected light value matches the target value, and the output current And a drive unit for driving the DC power supply circuit to have an amplification waveform of a reference wave.

  According to the LED lighting device, a continuous triangular or sawtooth current having a zero-peak amplitude is supplied to the LED, and the light amount depending on the current average value is controlled to be constant. This enables feedback control of the light amount in a state where a large margin is obtained with respect to the rated value of the LED current effective value compared to the pulse rectangular wave LED current, and the controllability of the LED current is improved. From another viewpoint, as compared with the LED lighting device using the pulse rectangular wave LED current, without increasing the current capacity of the LED lighting device (DC power supply circuit) or without increasing the number of elements of the LED It is possible to obtain more light quantity with a compact and simple configuration. Thus, in the LED lighting device, it is possible to supply the LED with an output current which is optimally determined in consideration of the balance of the average value, the effective value and the peak value.

  Further, the LED lighting device further includes a current detection unit that detects an output current and outputs an effective value of the output current as a current detection value, and the reference wave processing unit reduces the current detection value within the upper limit value or less. It is configured to control the peak value of the output reference wave. As a result, even in the configuration in which the triangular wave current is supplied to the LED, the lifetime of the LED can be reliably ensured.

  An LED lighting device according to a second aspect of the present invention includes: a DC power supply circuit that supplies an output current to the LED; a light amount detection unit that detects the light output of the LED and outputs an average value of the light output as a light amount detection value; A current detection unit that detects an output current and outputs an effective value of the output current as a current detection value, and a period in which a first reference wave consisting of a triangular wave or a sawtooth wave is equal to or greater than a second reference wave consisting of a constant DC wave Output the first reference wave as the output reference wave in a period in which the first reference wave is less than the second reference wave, and the detected current value reaches the upper limit value. And a reference wave for determining at least one of the peak value and the on-duty and the second reference wave in the first reference wave such that the light quantity detection value matches the target value and the current detection value matches the upper limit. Processing unit, output current is amplified wave of output reference wave And a driving unit for driving the DC power supply circuit so as to.

  According to the above-described LED lighting device, even if the light emission efficiency of the LED is lowered, the light amount and the current effective value depending on the current average value are controlled to be constant while the triangular wave or sawtooth current is supplied to the LED Therefore, the controllability of the LED current is improved. Thus, in the LED lighting device, the output current optimally determined in consideration of the balance between the average value, the effective value, and the peak value can be supplied to the LED.

  Further, the reference wave processing unit sets the first reference wave as a triangular wave or a sawtooth wave having a zero-peak amplitude and sets the value of the second reference wave to zero in a range where the current detection value is less than the upper limit. Configured as. Thereby, in the triangular or sawtooth LED current, the maximum peak value is always obtained regardless of the change in the luminous efficiency.

  The LED lighting device of the first or second aspect may further include notification means for notifying that the current detection value has reached the upper limit value. Since the situation where the current detection value reaches the upper limit value is a state in which the light emission efficiency of the LED is lowered, the user can judge the lifetime of the LED or the suitability of the LED installation environment (temperature state) by the above notification.

  Further, in the LED lighting device of the first or second aspect, it is preferable that the DC power supply circuit includes a DC / DC converter, and the frequency of the output reference wave is 1 kHz or more and 10 kHz or less. As described above, since the increase and decrease of the output current is controlled at a frequency lower than the drive frequency generally used in the output stage of the DC / DC converter, the current waveform can be reliably controlled with a simple configuration.

  The irradiation apparatus of this invention is equipped with one of the said LED lighting devices, and LED. Thus, as in the case of the above-described LED lighting device, an irradiation device capable of supplying the LED with an output current optimally determined in consideration of the balance between the average value, the effective value, and the peak value is realized. In addition, compared with the one using pulse rectangular wave LED current, without increasing the current capacity of the LED lighting device (DC power supply circuit) or without increasing the number of elements of the LED, ie, small and simple An irradiation device capable of obtaining a larger amount of light by the configuration is realized.

It is a block diagram of the LED lighting device by the 1st and 2nd embodiment of this invention, and the irradiation apparatus using the same. It is a figure which shows the LED current waveform in 1st Embodiment. It is a figure which shows an example of the power supply circuit in the LED lighting device of FIG. It is a figure which shows an example of the control circuit in the LED lighting device of 1st Embodiment. It is a figure which shows an example of the control circuit in the LED lighting device of 1st Embodiment. It is a figure which shows an example of the control circuit in the LED lighting device of 2nd Embodiment. It is a figure explaining the example of a LED current waveform in 2nd Embodiment. It is a figure explaining the example of a LED current waveform in 2nd Embodiment. It is a figure explaining the example of a LED current waveform in 2nd Embodiment. It is a figure explaining the example of a LED current waveform in 2nd Embodiment. FIG. 7 is a diagram showing an LED current waveform according to a modified example of the present invention. It is a figure which shows the LED lighting device by the modification of this invention. It is a figure which shows the LED current waveform of a comparative example.

First Embodiment
FIG. 1 shows a block diagram of an LED lighting device 1 according to a first embodiment of the present invention and an irradiation device 3 using the same. The irradiation device 3 includes an LED lighting device 1 and an LED 2. The LED lighting device 1 includes a DC power supply circuit 10 consisting of a main current circuit and a control circuit 20 consisting of a small signal circuit, converts the AC current from the AC power supply AC into a DC, and generates repetitive triangular waves as shown in FIG. A direct current is supplied to the LED 2. Details of this triangular wave will be described later. Although FIG. 1 illustrates two LED elements connected in series as the LEDs 2, an arbitrary number of LED elements may be connected in series or in series and parallel. The irradiation device 3 for emitting light from the LED 2 by the LED current of such a triangular wave is, for example, an irradiation device for curing or degenerating the irradiated object by ultraviolet light in printing, curing field etc. It is adopted as various irradiation devices such as irradiation devices.

  Here, with reference to FIG. 9 (comparative example) and FIG. 2, pulse rectangular waves and triangular waves (the amplitude is a zero-peak continuous triangular wave) having the same effective value Irms will be considered. FIG. 9 shows a pulse rectangular wave of peak value Ipp, on-duty D (%) and period T, and FIG. 2 shows a triangular wave of peak value Itp and period T (period T is effective value, average value and peak of each waveform) Does not affect the value). In the present specification, the continuous triangular wave or the continuous triangular wave refers to a triangular wave in which a period in which the amplitude value becomes zero as shown in FIG. 2 does not continue.

The average value Ipa and peak value Ipp of the pulse rectangular wave as shown in FIG.
Ipa = √D × Irms
Ipp = 1 / √D × Irms
It is.
The average value Ita and peak value Itp of the continuous triangular wave as shown in FIG.
Ita = √3 / 2 × Irms
Itp = √3 × Irms
It is.
And the on duty D of the pulse rectangular wave for obtaining the same peak value as the continuous triangular wave is
D = 1/3
It becomes. Therefore, when the pulse rectangular wave and the continuous triangular wave have the same effective value Irms and the same peak value √3 × Irms, the average value Ipa of the pulse rectangular wave is
Ipa = 1 / √3 × Irms ≒ 0.58 × Irms
While the average value Ita of the continuous triangular wave is
Ita = √3 / 2 × Irms ≒ 0.87 × Irms
And is higher than the average value Ipa of the pulse square wave.

  This means that when the current is applied up to the rated effective current of the LED 2 at the same peak current (peak illuminance), the average current Ita of the continuous triangular wave is higher (about 1.5 times) than the average current Ipa of the pulse rectangular wave, It means that more light intensity can be obtained by the LED current of the continuous triangular wave. Therefore, the LED current of the continuous triangular wave whose amplitude is zero-peak is useful as the current waveform in the above-described illumination device 3.

  The DC power supply circuit 10 includes a rectifier circuit 11 and a DC / DC converter 12. An example of the DC power supply circuit 10 is shown in FIG. The rectifier circuit 11 is composed of a diode bridge and full-wave rectifies the input voltage. In addition, a noise filter, a current fuse, etc. are connected to the front | former stage of a diode bridge as needed. Further, when the input power supply is a direct current power supply, the rectifier circuit 11 may not be necessary. In this example, the DC / DC converter 12 includes a power factor correction circuit 120 (boost chopper circuit) and a buck chopper circuit 130.

  Power factor correction circuit 120 includes an input capacitor 121, an inductor 122, a switching element 123, a diode 124 and a capacitor 125. The step-down chopper circuit 130 includes a switching element 131, an inductor 132, a diode 133, a capacitor 134 and a current detection resistor 135. As will be described in detail later, the switching elements 123 and 131 are PWM-driven by the drive unit 28 of the control circuit 20 with a predetermined ON width. In the power factor correction circuit 120, energy is stored in the inductor 122 during the on period of the switching element 123, and the energy is charged to the capacitor 125 through the diode 124 during the off period of the switching element 123. In the step-down chopper circuit 130, while the switching element 131 is on, an output current flows through the capacitor 134 → the switching element 131 → the inductor 132 → the LED2 → the current detection resistor 135, and energy is stored in the inductor 132. While the switching element 131 is off, an output current flows through the inductor 132 → the LED2 → the current detection resistor 135 → the diode 133 based on the energy stored in the inductor 132. Capacitor 134 smoothes the output voltage and current.

  The current detection resistor 135 is a low resistance element and is connected between the cathode end of the LED 2 and the low potential end of the capacitor 134. A voltage corresponding to the current flowing through the LED 2 is generated at both ends of the current detection resistor 135, and the voltage value substantially becomes a detection value of the effective value of the output current (LED current) of the DC / DC converter 12. The current detection resistor 135 constitutes a part of a current detection unit 23 described later.

  Returning to FIG. 1, the control circuit 20 will be described. The control circuit 20 has a triangular wave generation unit 21, a light amount detection unit 22, a current detection unit 23, a reference wave processing unit 24, and a drive unit 28. The reference wave processing unit 24 includes a light amount feedback unit 25, a current feedback unit 26 and an arithmetic unit. Including 27. The purpose of processing by the control circuit 20 is, as described above, on the premise that the LED current is a continuous triangular wave, that the effective value of the LED current does not exceed the rating of the LED 2 (to ensure the lifetime) The light amount depending on the average value is to be a desired value.

  The triangular wave generation unit 21 generates a continuous triangular input wave, and inputs it to the calculation unit 27 of the reference wave processing unit 24. The triangular wave generation unit 21 generates an input reference wave of a triangular wave by, for example, filtering the pulse rectangular wave generated by the oscillator with an integration circuit. The frequency of the input reference wave may be about 1 kHz to 10 kHz.

  The light amount detection unit 22 includes a light receiving element that converts the intensity of the detection light into an electric signal, and an integration circuit that integrates (smoothing) the electric signal. The light receiving element is disposed at a position where it can take in part of the irradiation light of the LED 2. The smoothed electric signal obtained by the light amount detection unit 22 indicates the average value (light amount) of the light output of the LED 2, which depends on the average value of the LED current. A detection value (hereinafter referred to as “light amount detection value”) obtained by the light amount detection unit 22 is input to the light amount feedback unit 25 of the reference wave processing unit 24.

  The current detection unit 23 acquires a voltage generated in the current detection resistor 135 described above. The voltage obtained by the current detection unit 23 substantially indicates the effective value of the LED current. A detection value (hereinafter, referred to as “current detection value”) obtained by the current detection unit 23 is input to the current feedback unit 26 of the reference wave processing unit 24.

  The reference wave processing unit 24 generates an output reference wave whose amplitude is zero-peak based on the input reference wave input from the triangular wave generation unit 21 and inputs the generated output reference wave to the drive unit 28. The peak value of the output reference wave is determined so that the light quantity detection value matches the target value in the range of not more than the upper limit value. That is, the output reference wave is a continuous triangular wave whose amplitude is zero-peak, and its peak value is controlled. Since the frequency of the output reference wave is the same as that of the input reference wave (1 kHz to 10 kHz), the output is performed at a frequency lower than the drive frequency (tens of kHz to hundreds of kHz) generally used in switching of the DC / DC converter 21. Control of increase and decrease of the current is performed, and the current waveform can be reliably controlled with a simple configuration.

  The structural example of the reference wave process part 24 is shown to FIG. 4A and 4B. As a rough outline, in the reference wave processing unit 24, the light amount feedback unit 25 is a circuit for feedback control of the light amount (substantially the average value of the LED current), and the current feedback unit 26 is an output current (substantially the LED current Circuit for feedback control of value), and one of the feedback control is selected in the operation unit 27. Then, in the operation unit 27, an output reference wave is generated according to the input reference wave from the triangular wave generation unit 21 and the feedback result of the light quantity feedback unit 25 or the current feedback unit 26. The capacitance of the capacitor 134 is appropriately set so as to pass the current ripple caused by the output reference wave without filtering while filtering (smoothing) the current ripple caused by the drive frequency.

First, the configuration shown in FIG. 4A will be described.
The light quantity feedback unit 25 includes an operational amplifier 250. The light quantity detection value detected by the light quantity detection unit 22 is input to the negative input terminal (-) of the operational amplifier 250, and a voltage corresponding to the target value of the light quantity is input from the voltage source 251 to the positive input terminal (+). . A feedback element 252 (a resistor, a capacitor, or a series circuit or a parallel circuit of these, hereinafter the same) is connected between the negative input terminal and the output terminal of the operational amplifier 250. The operational amplifier 250 amplifies and outputs an error between the current detection value input to the negative input terminal and the current target value input to the positive input terminal. In other words, when the diode 275 of the selection circuit 274 is turned on and light amount feedback is selected, the peak value of the output reference wave is set by the operational amplifier 250 and the calculation unit 27 so that the light amount detection value matches the target value. It is determined.

  The current feedback unit 26 includes an operational amplifier 260. The current detection value detected by the current detection unit 23 is input to the negative input terminal (-) of the operational amplifier 260, and the voltage corresponding to the upper limit value of the LED current effective value from the voltage source 261 is input to the positive input terminal (+). It is input. A feedback element 262 is also connected between the negative input terminal and the output terminal of the operational amplifier 260. The operational amplifier 260 amplifies and outputs an error between the voltage detection value input to the negative input terminal and the charge setting value input to the positive input terminal. In other words, when the diode 276 of the selection circuit 274 is turned on and output current feedback is selected, the peak value of the output reference wave is set so that the current detection value matches the upper limit value by the operational amplifier 260 and the operation unit 27. Is determined.

  Arithmetic unit 27 includes a CPU 270, a memory 273 and a selection circuit 274. As described above, the selection circuit 274 is formed of a diode OR circuit including the diodes 275 and 276, and is turned on to the output terminal voltage of the operational amplifier 250 or the output terminal voltage of the operational amplifier 260, whichever is lower. The common anode of the diode OR circuit is connected to the input port of the CPU 270. The CPU 270 is, for example, a microcomputer, and the memory 273 is a memory such as a ROM, a RAM, etc. for storing data, programs and the like.

  The configuration shown in FIG. 4B is different from the configuration shown in FIG. 4A in that the feedback by the light amount feedback unit 25 and the feedback selection by the current feedback unit 26 are performed by software in the CPU 270. Thus, the processing performed in the configuration shown in FIG. 4B is substantially the same as the processing described above with respect to FIG. 4A.

  In either case of FIG. 4A or FIG. 4B, the output value of the output current feedback by the operational amplifier 260 is substantially fixed to logic high while the light intensity feedback by the operational amplifier 250 is performed, and the output current feedback by the operational amplifier 260 is During operation, the output value of the light intensity feedback by the op amp 250 is substantially fixed at logic high. Then, the CPU 270 decreases / increases the peak value of the output reference wave with respect to the increase / decrease of the output value of the operational amplifier 250 or 260 in the feedback control being executed.

  The drive unit 28 drives the DC / DC converter 12 so that the output current has an amplified waveform of the output reference wave input from the reference wave processing unit 24 (the operation unit 27). That is, the drive unit 28 PWM drives the switching element 131 such that the DC / DC converter 12 outputs the output current of the continuous triangular wave having the amplitude of zero-peak and the peak value as a result of light amount feedback or output current feedback. . More specifically, in PWM control of the switching element 131, the drive unit 28 increases the ON width at the rising edge (from zero to peak) of the triangular wave of the output reference wave, and at the falling edge (from peak to zero). ) Reduce the on width. The drive unit 28 PWM drives the switching element 123 such that the output voltage of the power factor correction circuit 120 is equal to or more than the total value of the forward voltages Vf of the LEDs 2.

  In an actual operation, for example, feedback control is switched according to a change in luminous efficiency caused by a cumulative use time of the LED 2, a change in ambient temperature, and the like. Generally, in LEDs, the amount of light for the same LED current decreases with time and decreases with increasing temperature. As a rough outline, when the cumulative use time of LED 2 is relatively short, or the ambient temperature is relatively low, the luminous efficiency is relatively high, and there is a margin for the upper limit of the effective value of the LED current. (Feedback of substantially current average value) is selected. On the other hand, when the accumulated use time of the LED 2 is relatively long or the ambient temperature is relatively high, the luminous efficiency is relatively low, and output current feedback (feedback of substantially the current effective value) is selected. As described above, while the light amount feedback is selected, control is performed so that the peak value of the output reference wave is increased or decreased, and while the output current feedback is selected, the output reference wave is fixed.

  As described above, in the LED lighting device 1 of this embodiment, the DC power supply circuit 10 supplies the output current to the LED 2, and the light amount detection unit 22 detects the light output of the LED 2 and detects the average value of the light output Output as Then, the reference wave processing unit 24 generates an output reference wave of a triangular wave with a continuous amplitude of zero-peak, and determines the peak value of the output reference wave so that the light quantity detection value matches the target value. Thus, the DC power supply circuit 10 is driven such that the output current has an amplified waveform of the output reference wave. Thus, the current of the continuous triangular wave whose amplitude is zero-peak is supplied to the LED 2, and the light amount depending on the current average value is controlled to be constant. This enables feedback control of the light amount in a state where a large margin is obtained with respect to the rated value of the LED current effective value compared to the pulse rectangular wave LED current, and the controllability of the LED current is improved. From another perspective, the current capacity of the LED lighting device 1 (DC power supply circuit 10) is not increased, or the number of elements of the LED 2 is increased, as compared to an LED lighting device in which pulse rectangular wave LED current is employed. Therefore, it is possible to obtain a larger amount of light with a compact and simple configuration. Thus, in the LED lighting device 1 and the irradiation device 3, it is possible to supply the LED 2 with an output current that is optimally determined in consideration of the balance of the average value, the effective value, and the peak value.

  Further, since the reference wave processing unit 24 is configured to control the peak value of the output reference wave in a range in which the effective value of the LED current detected by the current detection unit 23 is equal to or less than the upper limit (rated value), Even in the configuration in which the triangular wave current is supplied to the LED 2, the life of the LED 2 is reliably ensured.

Second Embodiment
Although the first embodiment shows a configuration in which the LED current has a continuous triangular wave with a zero-peak amplitude, in the present embodiment, the LED current has a composite waveform of a triangular wave and a constant DC wave in a specific case. Indicates In the LED lighting device 1 of the present embodiment, the processing relating to the reference wave in the computing unit of the control circuit 20, in particular, the processing after the current detection value reaches the upper limit differs from that of the first embodiment.

  The block diagram of the LED lighting device 1 of the present embodiment and the irradiation device 3 using the same are shown in the first embodiment except that the operation unit 29 is employed instead of the operation unit 27 in the control circuit 20. It is similar to the block diagram of FIG. Hereinafter, the same reference numerals are given to the same components, and the detailed description thereof is omitted. Further, in the reference wave processing unit 24 (calculation unit 29), the same processing as in the first embodiment until the effective value of the LED current reaches the upper limit, ie, the light amount feedback by the light amount feedback unit 25 (substantially Feedback of the average value of the current is performed.

  As shown in FIG. 5, the calculation unit 29 comprises a CPU 290 and a memory 293, and the CPU 290 includes a reference wave synthesis unit 291 and a synthesis ratio adjustment unit 292. The CPU 290 is, for example, a microcomputer, and the memory 293 is a memory such as a ROM, a RAM, etc. for storing data, programs and the like.

  The reference wave synthesis unit 291 synthesizes a triangular reference wave consisting of a triangular wave whose amplitude is zero-peak based on the input reference wave from the triangular wave generation unit 21 and a constant reference wave consisting of a constant DC wave (constant value). Specifically, the reference wave synthesis unit 291 outputs a triangular reference wave in a period in which the triangular reference wave is equal to or greater than a fixed reference wave, a fixed reference wave in a period in which the triangular reference wave is less than the fixed reference wave, and Output as a wave. Thereby, a composite wave in which a triangular wave and a constant DC wave alternately appear or a composite wave in which a triangular wave is superimposed on the constant DC wave is generated as an output reference wave (the output current waveform corresponding to these output reference waves is described later 6A-6D)). The frequency of the output reference wave determined by the triangular reference wave may be about 1 kHz to 10 kHz, which is the same as the frequency of the input reference wave, as in the first embodiment.

  When the current detection value reaches the upper limit value, the combination ratio adjustment unit 292 causes the peak value and the on-duty of the triangular reference wave to match the light intensity detection value to the target value and the current detection value to the upper limit value. And the value of the constant reference wave.

We will now consider constant DC waves (those with an amplitude of zero) and continuous triangular waves (those with an amplitude of zero-peak) with the same effective value Irms.
The average value Ica of a constant DC wave is
Ica = Irms
It is.
The average value Ita of the triangular wave is, as described in the first embodiment,
Ita = √3 / 2 × Irms
And is smaller than the average value Ica of the constant DC wave.

  That is, in the state where the effective value of the LED current has reached the upper limit value (that is, the state where the upper limit value is constant), the constant LED current is higher in average value than the continuous triangular LED current More light quantity will be obtained by the constant LED current. Therefore, under the premise that the effective value of the LED current is fixed to the upper limit constant, as the ratio of the constant reference wave to the triangular reference wave in the output reference wave increases, the peak value decreases but the average value increases. That is, even if the effective value of the LED current is fixed to the upper limit value due to the decrease in the luminous efficiency, the target light of the LED 2 is increased by increasing the ratio of the constant reference wave to the triangular reference wave. The average value of the output (the light intensity by the target current average value) is obtained.

  Based on the above, as the light emission efficiency of the LED 2 becomes lower than a predetermined value (a value corresponding to the upper limit value of the current effective value) and the combination ratio adjustment unit 292 further decreases, the current detection value (current effective value) and the light amount The peak value or on-duty of the triangular reference wave is decreased and the value of the constant reference wave is increased so that the detected value (current average value) becomes constant. 6A to 6D show examples of the output current (LED current) controlled by the reference wave processing unit 24 (in particular, the combination ratio adjustment unit 292). In each of the drawings, the drawings are not limited to the dimensions.

  In the example of FIG. 6A, the light emission efficiency of the LED 2 is assumed to decrease from the upper stage (S1) to the lower stage (S3). When the effective value of the LED current has reached the upper limit value (S1), only the amplification current i1 of the triangular reference wave appears and its peak value is I1 (in a state where the luminous efficiency is higher than that of the state (S1) The peak value is lower than I1 (the same applies hereinafter). After that, in a state (S2) where the luminous efficiency of the LED 2 is lowered, the peak value of the amplification current i1 of the triangular reference wave is reduced from I1 to I2, and the amplification current i2 of the constant value I3 by the constant reference wave appears. The LED current) has a composite waveform of the amplification currents i1 and i2. After that, in a state where the light emission efficiency of the LED 2 is further reduced (S3), the peak value of the amplification current i1 of the triangular reference wave is further reduced from I2 to I4 in the synthesized waveform, and the value of the amplification current i2 of the constant reference wave is I3. To I5.

  In the example of FIG. 6B, the light emission efficiency of the LED 2 is assumed to decrease from the upper stage (S1) to the lower stage (S3). In the state (S1) in which the effective value of the LED current has reached the upper limit value, only the amplification current i1 of the triangular reference wave appears, and its peak value is I1. Thereafter, in a state where the light emission efficiency of the LED 2 is lowered (S2), the on-duty is reduced from 100% to D1% while the peak value of the amplification current i1 of the triangular reference wave is maintained at I1. Further, an amplification current i2 of a constant value I6 due to a constant reference wave appears, and the output current (LED current) becomes a composite waveform of the amplification currents i1 and i2. Thereafter, in the state (S3) where the luminous efficiency of the LED 2 is further reduced, the on-duty of the peak current of the triangular reference wave is further changed from D1% to D2% with the peak value of the triangular current is maintained at I1. The value is reduced, and the value of the amplification current i2 of the constant reference wave is raised from I6 to I7.

  In the example of FIG. 6C, the light emission efficiency of the LED 2 is assumed to decrease from the upper stage (S1) to the lower stage (S3). In the state (S1) in which the effective value of the LED current has reached the upper limit value, only the amplification current i1 of the triangular reference wave appears, and its peak value is I1. Then, in the state (S2) where the luminous efficiency of LED2 fell, the peak value is reduced from I1 to I8 in the state where the inclination of the triangular reference wave is maintained (in other words, the inclination of the triangular reference wave is maintained In the situation its on-duty is reduced). Also, an amplification current i2 of a constant value I9 by a constant reference wave appears, and the output current (LED current) becomes a composite waveform of the amplification currents i1 and i2. Thereafter, in a state (S3) where the luminous efficiency of LED 2 is further lowered, the peak value is further reduced from I8 to I10 in a state where the slope of the triangular reference wave is maintained in the composite waveform (in other words, With the inclination maintained, the on-duty is further reduced), and the value of the amplification current i2 of the constant reference wave is raised from I9 to I11.

  In the example of FIG. 6D, the light emission efficiency of the LED 2 is assumed to decrease from the upper stage (S1) to the lower stage (S3). In the state (S1) in which the effective value of the LED current has reached the upper limit value, only the amplification current i1 of the triangular reference wave appears, and its peak value is I1. Thereafter, in a state (S2) in which the light emission efficiency of the LED 2 decreases, the peak value of the amplification current i1 of the triangular reference wave is reduced from I1 to I12 and the bottom value is increased from 0 to I13, and its amplitude is reduced. . In other words, the output current (LED current) has a composite waveform in which the amplification current i1 of the amplitude I12-I13 is offset by the amplification current i2 of the constant value I13. Thereafter, in a state (S3) where the luminous efficiency of the LED 2 is further reduced, the peak value of the amplification current i1 of the triangular reference wave is further reduced to I12 to I14, and the bottom value is further increased to I13 to I15. Reduced. In other words, the output current (LED current) has a composite waveform in which the amplification current i1 of the amplitude I14-I15 is offset by the amplification current i2 of the constant value I15.

  In any processing of the output current, when the luminous efficiency of the LED 2 is significantly reduced, the ratio of the triangular wave in the LED current waveform is significantly reduced, and the effect of the LED irradiation by the triangular wave current which is the original purpose Could be reduced. Therefore, for example, as in each state (S3) of FIG. 6A to FIG. 6D, when the light emission efficiency of the LED 2 falls below the lower limit (for example, when the peak value of the triangular reference wave falls below a predetermined value or When the value exceeds a predetermined value, it is preferable that the control circuit 20 not operate the DC / DC converter 12.

  As described above, in the LED lighting device 1 of this embodiment, the DC power supply circuit 10 supplies the output current to the LED 2, and the light amount detection unit 22 detects the light output of the LED 2 and detects the average value of the light output The current detection unit 23 detects the output current, and outputs the effective value of the output current as a current detection value. Then, the reference wave processing unit 24 outputs the triangular reference wave as an output reference wave in a period in which the triangular reference wave is less than the fixed reference wave and in a period in which the triangular reference wave is less than the fixed reference wave. When the current detection value reaches the upper limit value, at least one of the peak value and the on-duty and the constant reference in the triangular reference wave such that the light intensity detection value matches the target value and the current detection value matches the upper limit value Determine the wave value. Then, the drive unit 28 drives the DC power supply circuit 10 such that the output current has an amplified waveform of the output reference wave. As described above, even when the light emission efficiency of the LED 2 is lowered, the light amount and the current effective value depending on the current average value are controlled to be constant while the triangular wave or sawtooth current is supplied to the LED 2. Controllability of current is improved. Therefore, in the LED lighting device 1 and the irradiation device 3, it is possible to supply the LED 2 with an output current optimally determined in consideration of the balance of the average value, the effective value, and the peak value.

  Also, as described above, in the range where the current detection value is less than the upper limit, the reference wave processing unit is such that the triangular reference wave is a continuous triangular wave having a zero-peak amplitude, and the value of the constant reference wave is zero. 24 works. Thereby, in the triangular LED current, the maximum peak value is always obtained regardless of the change in the luminous efficiency.

<Modification>
Although the preferred embodiments of the present invention have been described above, the present invention can be modified in various aspects, for example, as described below.

(1) Modification of LED Current Waveform In the first embodiment described above, although the symmetrical continuous triangular LED current in which the absolute values of the rising slope and the falling slope are equal is shown, the rising slope and the falling The absolute value of the slope may employ different asymmetrical continuous triangular LED currents. Also, the LED current may be a continuous sawtooth whose amplitude is zero-peak as shown in FIG. Also in the second embodiment, the triangular reference wave may be an asymmetric triangular wave having different absolute values of the rising slope and the falling slope, or may be a sawtooth wave.

(2) Modification of DC Power Supply Circuit 10 In the above embodiment, the DC / DC converter 12 of the DC power supply circuit 10 is configured to include the power factor improvement circuit 120 and the step-down chopper circuit 130. It is not restricted to this. For example, a flyback circuit may be used instead of the step-down chopper circuit 130. Also, for the purpose of flash light irradiation in a relatively short time (about 100 ms to 500 ms), a storage element and its charging circuit are provided instead of the power factor improvement circuit 120, and the step-down chopper circuit 130 is supplied with power from the storage element. You may However, also in these cases, the capacity of the capacitor on the output side is appropriately set in consideration of the controllability of the output current (increase / decrease at about 1 kHz to 10 kHz). Furthermore, the DC power supply circuit 10 may be a stabilized power supply or the like capable of programming the output current.

(3) Addition of Notification Means As shown in FIG. 9, in each of the above-described embodiments, when the detected current value (LED current effective value) reaches the upper limit value, the notification unit 30 is provided to notify the user to that effect. It may be done. In this case, when it is determined based on the output of the current feedback unit 26 that the current detection value has reached the upper limit value, the calculation units 27 and 29 operate the notification unit 30, whereby the notification unit 30 executes the notification operation. Do. In the second embodiment, the calculating unit 29 notifies when the peak value of the triangular reference wave falls below the predetermined value or the value of the fixed reference wave exceeds the predetermined value by the operation of the combining ratio adjustment unit 292. The unit 30 may be operated, and the notification unit 30 may execute a further notification operation.

  The notification unit 30 may be a notification unit by light emission display by an LED or the like, visual display by a liquid crystal display or the like, audible display by a buzzer, voice etc., or a combination thereof. For example, when the screen of the operation panel is provided in the irradiation device 3, the notification may be performed on the screen. As described above, the current detection value reaches the upper limit value because the light emission efficiency of the LED 2 is lowered, and the notification unit 30 notifies the user of the life of the LED 2 (the replacement timing of the LED 2) or the installation environment It is possible to determine (appropriateness of the temperature condition).

1 LED lighting device 2 LED
DESCRIPTION OF SYMBOLS 3 irradiation apparatus 10 DC power supply circuit 12 DC / DC converter 20 control circuit 22 light quantity detection part 23 electric current detection part 24 reference wave processing part 28 drive part 30 alerting | reporting part

Claims (5)

LED lighting device,
DC power supply circuit that supplies output current to LED;
A light amount detection unit that detects a light output of the LED and outputs an average value of the light output as a light amount detection value;
A current detection unit that detects the output current and outputs an effective value of the output current as a current detection value;
The first reference wave is a period during which the first reference wave consisting of a triangular wave or a sawtooth wave is equal to or more than the second reference wave consisting of a constant DC wave, and the first reference wave is the second reference wave The second reference wave is output as an output reference wave in a period of less than, and when the current detection value reaches the upper limit value, the light amount detection value matches the target value and the current detection value is the A reference wave processing unit that determines at least one of the peak value and the on duty of the first reference wave and the value of the second reference wave so as to coincide with the upper limit value;
An LED lighting device comprising: a drive unit for driving the DC power supply circuit such that the output current has an amplified waveform of the output reference wave. The LED lighting device according to claim 1 , wherein the reference wave processing unit causes the first reference wave to have a zero-peak continuous triangular wave or sawtooth in a range where the detected current value is less than the upper limit. LED lighting device, which is configured to zero the value of the second reference wave as a wave. The LED lighting device according to claim 2, further comprising notification means for notifying that the current detection value has reached the upper limit value. The DC power supply circuit comprises a DC / DC converter, the frequency of the output reference wave is 1kHz or 10kHz or less, LED lighting device according to any one of claims 1 or et 3. Irradiation apparatus having an LED lighting device according to any one of claims 1 or et 4, and the LED.

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