JP2014143017A - Lighting device, and illuminating fixture and illumination system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device capable of suppressing current flowing in a light-emitting element from rising excessively in a state that there are abnormalities in an electronic component, and to provide an illuminating fixture and an illumination system using the same.SOLUTION: A control circuit 12 comprises: a control IC 121 turning off a switching element Q1 when current flowing in a primary coil N1 of a transformer T1 reaches a predetermined value; a secondary coil N2 detecting current flowing in the primary coil N1; and a determination part 123 determining an ON timing of the switching element Q1 on the basis of a clock signal from a clock signal generator 122 and a detection result of the secondary coil N2. The determination part 123, when it is detected that the current flowing in the primary coil N1 does not reach zero by the secondary coil N2 at the time when one cycle of the clock signal is terminated, continues an off state of the switching element Q1 without turning on the switching element Q1 until when the next one cycle is terminated, and when it is detected that the current becomes zero by the secondary coil N2, turns on the switching element Q1.

Description

  The present invention relates to a lighting device, a lighting fixture using the lighting device, and a lighting system.

  Conventionally, various lighting devices for lighting a light emitting element such as a light emitting diode (LED) have been provided (see, for example, Patent Document 1), and an example thereof will be described below.

  FIG. 7 is a schematic circuit diagram showing an example of a conventional lighting device 1. The lighting device 1 includes a rectifier circuit 7 that rectifies the commercial power supply 100, a power factor improvement circuit 8 that converts the output voltage of the rectifier circuit 7 into a desired voltage, and an output voltage of the power factor improvement circuit 8 to the LED module 10. A step-down chopper circuit 11 that steps down to an appropriate voltage and a control IC 121 that controls the operation of the step-down chopper circuit 11 are provided. The step-down chopper circuit 11 includes an inductor L1 connected in series with the LED module 10, and a switching element Q1 connected in series between the series circuit including the LED module 10 and the inductor L1 and the power factor correction circuit 8. And a diode D1 connected in parallel to the series circuit.

  In such a lighting device 1, there are three types of operation modes, continuous mode (CCM), critical mode (BCM), and discontinuous mode (DCM), with respect to the current flowing through inductor L1. In the continuous mode, since the inductance value of the inductor L1 is generally large, the inductor L1 is likely to be large, and when the LED module 10 is dimmed, the dimming is performed by varying the on-duty ratio of the switching element Q1. PWM control is performed.

  Further, when performing PWM control in the critical mode, the inductor L1 becomes large when the frequency of the PWM signal is low (less than 40 kHz), and noise is generated in the inductor L1 at frequencies in the audible range, and at frequencies near 30 to 40 kHz, The ripple component having a frequency equal to the frequency of the PWM signal superimposed on the current waveform flowing in the LED module 10 may interfere with an infrared remote controller or the like used in other devices, and the smoothing capacitor C1 needs to have a large capacity. .

  Further, when the frequency is increased in order to reduce the size of the inductor L1 and the smoothing capacitor C1, the on / off frequency of the switching element Q1 increases as the current flowing through the LED module 10 decreases due to dimming. The on-duty ratio approaches zero. As a result, the operation may become unstable due to the delay time in the control IC 121 that controls the on / off of the switching element Q1, the driving capability of the switching element Q1, and the like.

  On the other hand, in the discontinuous mode, the above-described problems are solved, and the switching element Q1 is turned on when controlling the current flowing through the LED module 10 to be low even if the inductance value of the inductor L1 is relatively small. / Off frequency is also lowered. And since the ON / OFF frequency of the switching element Q1 becomes low, it becomes possible to make the ON period of the switching element Q1 comparatively long. In the discontinuous mode, the control can be simplified when the on / off frequency of the switching element Q1 is set to a constant frequency.

JP 2009-240114 A

  In the lighting device 1 shown in FIG. 7 described above, when the current flowing through the LED module 10 is set to a discontinuous mode with a constant frequency, for example, when the COMP terminal of the control IC 121 is released, the multiplier output inside the control IC 121 is It sticks to Hi, and the current flowing through the inductor L1 rises more than necessary. By the way, the control IC 121 is set with a clamp voltage for preventing the switching element Q1 from being kept on. When the voltage value corresponding to the current flowing through the inductor L1 reaches the clamp voltage, the control IC 121 is set. The Lo signal is output from the OUT terminal of the, and the switching element Q1 is turned off.

  However, the clamp voltage is set to a considerably larger value than the voltage value (voltage value corresponding to the current flowing through the inductor L1) input to the CS terminal of the control IC 121 in a normal use state. Therefore, in this case, the time until the clamp voltage is reached is the on-time, and the off-time is also determined by the on-time. In this lighting device 1, the switching element Q <b> 1 is turned on every time one cycle is passed by the clock signal output from the clock signal generation unit 122, so that the current flowing through the inductor L <b> 1 becomes a continuous mode. There is a problem that an excessive current flows through the LED module 10.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a lighting device that suppresses an excessive increase in the current flowing through the light-emitting element in a state where an abnormality has occurred in the electronic component, and the lighting device It is in providing the lighting fixture and lighting system using this.

  The lighting device of the present invention includes an inductor connected in series to the light emitting element, a switching element connected in series between the series circuit of the light emitting element and the inductor and the DC power supply, and a parallel connection to the series circuit. And a step-down chopper circuit having a rectifying element connected in a direction to discharge the stored energy of the inductor to the light emitting element when the switching element is turned off, and a control circuit for turning on / off the switching element. The control circuit includes a signal output unit that outputs a rectangular wave signal having a constant frequency, a first control unit that turns off the switching element when the current flowing through the inductor reaches a predetermined value when the switching element is turned on, and the switching element is turned off. A current detection unit that detects a state of a current flowing through the inductor during a certain period, and a second control unit that determines the on-timing of the switching element based on the detection result of the rectangular wave signal and the current detection unit. When the second control unit detects that the current flowing through the inductor does not reach zero at the end of one cycle of the rectangular wave signal, the second control unit does not turn on the switching element until at least the end of the next cycle. If the current detection unit detects that the current flowing through the inductor becomes zero at the end of one cycle of the rectangular wave signal, the switching element is turned on.

  The lighting device of the present invention includes a transformer having at least a primary winding and a secondary winding, a switching element connected in series between the primary winding and a DC power supply, and connected in series to the secondary winding. And a capacitor connected in parallel to the light emitting element, and a secondary circuit and a capacitor to form a series circuit, which is connected in a direction in which the switching element is cut off when the switching element is turned on and is turned on when the switching element is turned off. A converter circuit including a rectifying element and a control circuit for turning on / off the switching element. The control circuit includes a signal output unit that outputs a rectangular wave signal having a constant frequency, a first control unit that turns off the switching element when a current flowing through the primary winding reaches a predetermined value when the switching element is turned on, A current detection unit that detects a state of a current flowing in the secondary winding during the off-state, and a second control unit that determines the on-timing of the switching element based on the detection result of the rectangular wave signal and the current detection unit It has. When the second control unit detects that the current flowing through the secondary winding does not reach zero at the end of one cycle of the rectangular wave signal, the second control unit does not turn on the switching element until at least the end of the next one cycle. And the switching element is turned on when the current detection unit detects that the current flowing through the secondary winding becomes zero at the end of one cycle of the rectangular wave signal.

  The lighting fixture of the present invention includes the above lighting device and a light emitting element to which lighting power is supplied from the lighting device.

  The lighting system of the present invention includes the above-described lighting fixture.

  If the current flowing through the inductor at the end of one cycle of the rectangular wave signal is not zero, the switching element is kept off until at least the end of the next cycle, and the current flowing through the inductor at the end of one cycle of the rectangular wave signal Since the switching element is turned on when the value is zero, for example, when the electronic component becomes open or short-circuited due to mounting errors or aging of the electronic components constituting the control circuit, the inductor The flowing current can be set to the discontinuous mode, and as a result, it is possible to suppress an excessive increase in the current flowing through the light emitting element.

(A), (b) is a schematic circuit diagram which shows an example of the lighting device of Embodiment 1. FIG. It is a flowchart for demonstrating the operation | movement same as the above. (A)-(d) is a time chart for demonstrating operation | movement same as the above. (A)-(d) is another time chart for demonstrating an operation | movement same as the above. It is a schematic circuit diagram which shows an example of the lighting device of Embodiment 2. (A), (b) is sectional drawing which shows an example of the lighting fixture using the lighting device of Embodiment 1 or 2. FIG. It is a schematic circuit diagram which shows an example of the conventional lighting device.

  Embodiments of a lighting device, a lighting fixture using the lighting device, and a lighting system will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1A is a schematic circuit diagram illustrating an example of the lighting device 1 of the present embodiment. The lighting device 1 includes a rectifier circuit 7, a power factor correction circuit 8, a dimming circuit 9, a step-down chopper circuit 11, and a control circuit 12, and supplies lighting power corresponding to the dimming level to the LED module 10. Supply.

  The rectifier circuit 7 rectifies the AC voltage supplied from the commercial power supply 100 into a DC voltage, and the power factor correction circuit 8 converts the DC voltage output from the rectifier circuit 7 into a DC voltage having a desired voltage value. Note that the rectifier circuit 7 and the power factor correction circuit 8 have a conventionally well-known configuration and will not be described in detail. Here, in the present embodiment, the rectifier circuit 7 and the power factor correction circuit 8 constitute a DC power source.

  The dimming circuit 9 outputs a dimming signal for setting the dimming level of the LED module 10, and converts the dimming signal output from the dimming signal output unit 91 into a DC signal. And a signal converter 92 and an operational amplifier 93.

  A reference voltage corresponding to the DC signal generated by the signal converter 92 is input to the non-inverting input terminal of the operational amplifier 93, and a voltage signal corresponding to the current flowing through the LED module 10 is input to the inverting input terminal of the operational amplifier 93. Is entered. The operational amplifier 93 outputs an amplified signal obtained by amplifying the difference between the reference voltage and the voltage signal to the control IC 121 described later. The dimming signal output unit 91 described above may be provided integrally with the lighting device 1 or may be provided separately.

  The LED module 10 includes a plurality of (four in FIG. 1A) light emitting diodes (LEDs) connected in series, and is lit by DC power supplied from the step-down chopper circuit 11. Here, in the present embodiment, a light emitting element is constituted by each light emitting diode of the LED module 10.

  The step-down chopper circuit 11 includes a switching element Q1, a diode D1 (rectifier element), a transformer T1, and a smoothing capacitor C1. The step-down chopper circuit 11 supplies DC power corresponding to the dimming level set by the dimming circuit 9 described above. The generated DC power is output to the LED module 10.

  The switching element Q1 is made of, for example, an n-type MOSFET, and is connected to the output terminal on the high potential side of the power factor correction circuit 8, and is turned on / off according to the Hi signal or Lo signal output from the high side driver 124 described later. To do.

  The transformer T1 has a primary winding N1 and a secondary winding N2, and the primary winding N1 is connected in series to the LED module 10, and the secondary winding N2 is a current flowing through the primary winding N1. It is provided to detect the state of Here, in the present embodiment, the primary winding N1 constitutes an inductor, and the secondary winding N2 constitutes a current detection unit.

  The smoothing capacitor C <b> 1 is connected in parallel to the LED module 10, smoothes the DC power supplied via the primary winding N <b> 1, and outputs it to the LED module 10.

  The diode D1 is connected in parallel to the series circuit composed of the LED module 10 and the primary winding N1 of the transformer T1, and further releases the stored energy of the primary winding N1 to the LED module 10 when the switching element Q1 is turned off. It is connected in the direction (in the example shown in FIG. 1A, the anode is on the lower side and the cathode is on the upper side).

  The control circuit 12 includes a control IC 121, a clock signal generation unit 122, a determination unit 123, and a high side driver 124.

  The control IC 121 is composed of, for example, an IC (Toshiba TB6819AFG or the like) having the above-described critical mode function, and has a ZCD terminal, a CS terminal, a COMP terminal, and an OUT terminal. The Hi signal or Lo signal output from the determination unit 123 is input to the ZCD terminal of the control IC 121, and when the Lo signal is input, the Hi signal is output from the OUT terminal to the high side driver 124. The The high-side driver 124 that has received the Hi signal from the control IC 121 outputs the Hi signal to the switching element Q1, thereby turning on the switching element Q1.

  The amplified signal output from the operational amplifier 93 of the dimming circuit 9 is input to the COMP terminal of the control IC 121, and the control IC 121 receives a threshold value (predetermined) for the current flowing through the LED module 10 based on the amplified signal. Value) is set. A voltage signal corresponding to the current flowing through the LED module 10 (current flowing through the primary winding N1 of the transformer T1) is input to the CS terminal of the control IC 121, and the control IC 121 sets the voltage signal to the voltage level. When it reaches, the Lo signal is output from the OUT terminal to the high side driver 124. The high-side driver 124 that has received the Lo signal from the control IC 121 outputs the Lo signal to the switching element Q1, thereby turning off the switching element Q1. The resistor R1 connected in series with the LED module 10 is a resistor for detecting a current flowing through the LED module 10. Here, in the present embodiment, the control IC 121 constitutes a first control unit.

  The clock signal generation unit 122 generates a clock signal (rectangular wave signal) having a constant frequency (for example, 40 kHz), and outputs the generated clock signal to the determination unit 123. Here, in the present embodiment, the clock signal generation unit 122 constitutes a signal output unit.

  The determination unit 123 receives the clock signal generated by the clock signal generation unit 122, and further receives a voltage signal corresponding to the current flowing through the secondary winding N2 of the transformer T1. Then, the determination unit 123 detects the state of the current flowing through the primary winding N1 from the voltage signal, and determines the ON timing of the switching element Q1 based on the clock signal and the detection result. Details will be described later. Here, in the present embodiment, the determination unit 123 constitutes a second control unit.

  Next, the basic operation of the lighting device 1 will be described. When a switch (not shown) that activates the lighting device 1 is turned on, the rectifier circuit 7 rectifies the AC voltage supplied from the commercial power supply 100 into a DC voltage, and the power factor correction circuit 8 further than the rectifier circuit 7. The output DC voltage is converted into a DC voltage having a desired voltage value.

  The clock signal generation unit 122 generates a clock signal with a constant frequency (for example, 40 kHz), and outputs the generated clock signal to the determination unit 123. The voltage signal corresponding to the state of the current flowing through the primary winding N1 of the transformer T1 is input to the determination unit 123. Then, the determination unit 123 determines whether or not one cycle of the clock signal has ended (step S1 in FIG. 2), and the state of the current flowing through the primary winding N1 at the timing when one cycle of the clock signal ends. Is determined (step S2 in FIG. 2).

  At this time (before the step-down chopper circuit 11 is started), no current flows through the primary winding N1 and the secondary winding N2, and the voltage signal is not input to the determination unit 123. It is determined that the current flowing through the next winding N1 is zero, and a Lo signal is output to the control IC 121 (step S3 in FIG. 2). When the Lo signal from the determination unit 123 is input to the ZCD terminal, the control IC 121 outputs an ON signal (Hi signal) from the OUT terminal to the high side driver 124, and the high side driver 124 includes the switching element Q1. Outputs a Hi signal.

  As a result, the switching element Q1 is turned on, and a current flows through the primary winding N1 of the transformer T1 by the DC power output from the power factor correction circuit 8, thereby storing energy in the primary winding N1. The DC power is also supplied to the LED module 10, and the LED module 10 is lit at a dimming level corresponding to the DC power.

  When the switching element Q1 is turned on, a voltage signal corresponding to the current flowing through the LED module 10 is input to the CS terminal of the control IC 121 and the inverting input terminal of the operational amplifier 93, respectively. A reference voltage corresponding to the dimming signal output from the dimming signal output unit 91 is input to the non-inverting input terminal of the operational amplifier 93. The operational amplifier 93 amplifies the difference between the reference voltage and the voltage signal. The amplified signal is generated, and the generated amplified signal is output to the COMP terminal of the control IC 121.

  The control IC 121 sets a voltage level corresponding to the threshold value of the current flowing through the LED module 10 based on the amplified signal input to the COMP terminal, and when the voltage signal input to the CS terminal reaches the voltage level. Then, an off signal (Lo signal) for turning off the switching element Q1 is output from the OUT terminal to the high side driver 124. When the high-side driver 124 receives the off signal from the control IC 121, it outputs a Lo signal to the switching element Q1, thereby turning off the switching element Q1.

  When the switching element Q1 is turned off, the LED module 10 is turned on by the energy accumulated in the primary winding N1 of the transformer T1, and the current flowing through the primary winding N1 decreases with time. The determination unit 123 detects the state of the current flowing through the primary winding N1 by the secondary winding N2 at the timing when one cycle of the clock signal output from the clock signal generation unit 122 elapses (in FIG. 2). Steps S1 and S2), and if the current flowing through the primary winding N1 is not zero when one cycle of the clock signal has elapsed, the determination unit 123 continuously outputs the Hi signal to the control IC 121 ( Step S4 in FIG. If the current is zero when one cycle of the clock signal has elapsed, the determination unit 123 outputs a Lo signal to the control IC 121 (step S3 in FIG. 2), and the same processing is performed thereafter. The switching element Q1 is turned on.

  As described above, the LED module 10 is lit at a predetermined dimming level by repeating the on / off operation of the switching element Q1.

  Here, when the current flowing through the LED module 10 is larger than the threshold value, the voltage level of the voltage signal input to the inverting input terminal of the operational amplifier 93 via the resistor R1 rises, and the non-inverting input terminal of the operational amplifier 93 The voltage level of the voltage signal increases with respect to the reference voltage input to. As a result, the operational amplifier 93 performs a sink (sink current) operation, and the output voltage of the operational amplifier 93 decreases. When the output voltage of the operational amplifier 93 is lowered, the COMP terminal voltage of the control IC 121 is also lowered, and as a result, the voltage level set corresponding to the threshold value is also lowered.

  When the voltage level is lowered, the OFF timing of the switching element Q1 is advanced. As a result, the ON period of the switching element Q1 is shortened, and the current flowing through the LED module 10 is reduced. When the current flowing through the LED module 10 decreases, the voltage level of the voltage signal input to the inverting input terminal of the operational amplifier 93 decreases. As a result, the reference voltage input to the non-inverting input terminal of the operational amplifier 93 As a result, the sink operation of the operational amplifier 93 is stopped. Thereby, the LED module 10 is controlled according to the light control level.

  Further, in the lighting device 1 of the present embodiment, control is performed so that the current flowing through the LED module 10 increases as the reference voltage corresponding to the dimming signal output from the dimming signal output unit 91 increases, and the dimming signal output is performed. The current flowing through the LED module 10 is controlled to decrease as the reference voltage corresponding to the dimming signal output from the unit 91 decreases, and the light amount of the LED module 10 can be freely controlled according to the dimming signal. Can do.

  Here, when all lighting or dimming lighting is normally performed, as shown in FIG. 3 (b) or 3 (c), the LED module 10 is turned on until one cycle of the clock signal Sig1 elapses. This is a so-called discontinuous mode in which the flowing current I1 becomes zero. Therefore, in this case, the current I2 flowing through the LED module 10 does not increase excessively.

  By the way, an electronic component may be in an open state or a short circuit state due to a mistake during mounting or aging. As an example, when the COMP terminal of the control IC 121 constituting the control circuit 12 is opened, the multiplier output in the control IC 121 sticks to Hi, and the current flowing in the primary winding N1 of the transformer T1. I1 rises more than necessary. However, a clamp voltage is set in the control IC 121 to prevent the switching element Q1 from continuing to be turned on, and the voltage value of the voltage signal corresponding to the current I1 flowing through the primary winding N1 becomes the clamp voltage. When it reaches, the Lo signal is output from the OUT terminal of the control IC 121, and the switching element Q 1 is turned off via the high side driver 124.

  When the operation for determining whether or not the current I1 flowing through the LED module 10 is zero when one cycle of the clock signal Sig1 elapses, as shown in FIG. 3D, the time t1 when one cycle of the clock signal Sig1 elapses. At this time, the switching element Q1 is turned on, and the current I1 flowing through the primary winding N1 of the transformer T1 gradually increases. Thereafter, when the voltage value of the voltage signal corresponding to the current I1 reaches the clamp voltage, the switching element Q1 is turned off and the current I1 gradually decreases, but the next one cycle of the clock signal Sig1 elapses. At time t2, the current I1 is not zero. Moreover, since the switching element Q1 is turned on again at this timing, the current I1 rises again without becoming zero.

  Further, when the voltage value of the voltage signal corresponding to the current I1 reaches the clamp voltage, the switching element Q1 is turned off and the current I1 gradually decreases, but the next one cycle of the clock signal Sig1 elapses. At time t3, the current I1 is not zero. Moreover, since the switching element Q1 is turned on again at this timing, the current I1 rises again without becoming zero.

  As described above, when the operation of determining whether or not the current I1 is zero when one cycle of the clock signal Sig1 elapses, the current I1 flowing through the primary winding N1 of the transformer T1 becomes a continuous mode, As a result, as shown in FIG. 3D, the current I2 flowing through the LED module 10 is excessively increased. Note that Sig2 in FIGS. 3B, 3C, and 3D is a signal that the high-side driver 124 outputs to the switching element Q1.

  On the other hand, in the lighting device 1 of the present embodiment, as shown in FIG. 4C, at time t1 when one cycle of the clock signal Sig1 elapses, the voltage according to the current flowing through the secondary winding N2 of the transformer T1 The voltage value V1 of the signal is not zero. Therefore, the switching element Q1 remains off, and the energy I1 accumulated in the primary winding N1 is consumed by the LED module 10 to reduce the current I1 flowing through the primary winding N1 (FIG. 4 ( d)).

  At time t2 when the next one cycle of the clock signal Sig1 elapses, the voltage value V1 of the voltage signal is zero, and the current I1 flowing through the primary winding N1 is also zero at this timing. Accordingly, the switching element Q1 is turned on at this timing, and the current I1 flowing through the primary winding N1 rises again.

  Further, when the voltage value of the voltage signal corresponding to the current I1 reaches the clamp voltage, the switching element Q1 is turned off, and the energy accumulated in the primary winding N1 is consumed by the LED module 10 to be primary. The current I1 flowing through the winding N1 decreases. At time t3 when the next cycle of the clock signal Sig1 elapses, the voltage value V1 of the voltage signal is not zero, so the switching element Q1 remains off and the current I1 further decreases. Go. Similarly, the current I1 can be set to the discontinuous mode by repeating the on / off operation of the switching element Q1, and as a result, as shown in FIG. An excessive rise can be suppressed. Note that Sig3 in FIG. 4B is a signal output from the determination unit 123 to the control IC 121.

  FIG. 1B is a schematic circuit diagram showing another example of the lighting device 1. In FIG. 1A, the switching element Q1 is connected to the output terminal on the high voltage side of the power factor correction circuit 8, but in this example, the switching element Q1 is connected to the output terminal on the low voltage side of the power factor correction circuit 8. Yes. In this case, since the on / off of the switching element Q1 can be directly controlled by the on / off signal output from the OUT terminal of the control IC 121, the high side driver 124 is unnecessary. Other configurations and operations are the same as those of the lighting device 1 shown in FIG.

  According to the present embodiment, if the current I1 flowing through the primary winding N1 of the transformer T1 is not zero at the end of one cycle of the clock signal Sig1, the switching element Q1 is turned off at least until the end of the next one cycle. When the current I1 flowing through the primary winding N1 becomes zero at the end of one cycle of the clock signal Sig1, the switching element Q1 is turned on. Thereby, for example, even if the electronic component is opened or short-circuited due to mounting errors or aging of the electronic components constituting the control circuit 12, the current I1 flowing through the primary winding N1 is discontinuous mode. As a result, it is possible to suppress the current I2 flowing through the LED module 10 from rising excessively.

  Further, when the load voltage of the LED module 10 to be connected is smaller than the assumed load voltage and the load current is high, in the conventional lighting device 1, the current flowing through the primary winding N1 tends to be in the continuous mode. According to the lighting device 1 of the present embodiment, when the current flowing through the primary winding N1 is not zero at the end of one cycle of the clock signal Sig1, the primary winding is maintained in order to maintain the switching element Q1 in the off state. The current flowing through N1 can be surely set to the discontinuous mode or the critical mode.

  In the present embodiment, the control IC 121 is configured by an IC having a critical mode function. However, other ICs may be used as long as the same operation can be realized. Further, at least one of the dimming circuit 9, the clock signal generation unit 122, the determination unit 123, and the high-side driver 124 and the control IC 121 may be integrated to form one IC. Further, when the dimming signal output unit 91 is provided separately from the lighting device 1, the signal conversion unit 92 may be connected by a wired signal line, or the signal may be transmitted by a wireless signal such as an infrared signal. Transmission may be performed.

  When the dimming signal output unit 91 is provided integrally with the lighting device 1, the dimming signal output unit 91 is configured by a microcomputer or the like so that the dimming signal is output according to a predetermined program. Good. For example, time schedule control may be performed in which lighting is performed at a preset dimming ratio for a predetermined time of the day. Furthermore, in this embodiment, the timing at which the current flowing through the primary winding N1 becomes zero based on the voltage signal corresponding to the current flowing through the secondary winding N2 of the transformer T1 is detected. For example, the reverse direction of the diode D1 The timing at which the current flowing through the primary winding N1 becomes zero may be detected by detecting the voltage rise or the voltage drop across the switching element Q1, and further flowing through the primary winding N1. Any other device may be used as long as the timing at which the current becomes zero can be detected.

(Embodiment 2)
Embodiment 2 of the lighting device 1 will be described with reference to FIG. Although the step-down chopper circuit 11 is used in the lighting device 1 described in the first embodiment, the converter circuit 13 is used in the present embodiment. In addition, about another structure, it is the same as that of Embodiment 1, the same code | symbol is attached | subjected to the same component and description is abbreviate | omitted.

  The lighting device 1 according to the present embodiment includes a rectifier circuit 7, a power factor correction circuit 8, a dimming circuit 9, a control circuit 12, and a converter circuit 13, and supplies lighting power corresponding to the dimming level to the LED module. 10 is supplied. Here, also in the present embodiment, the rectifier circuit 7 and the power factor correction circuit 8 constitute a DC power source.

  The converter circuit 13 is a so-called flyback converter circuit, and includes a transformer T1, a switching element Q1, a smoothing capacitor C1, and a diode D1 (rectifier element), and is set by the dimming circuit 9. DC power corresponding to the dimming level is generated, and the generated DC power is output to the LED module 10.

  The transformer T1 includes a primary winding N1, a secondary winding N2, and a tertiary winding N3. The primary winding N1 is connected in series to the switching element Q1, and the primary winding N1 and the switching element A series circuit composed of Q1 is connected between the outputs of the power factor correction circuit 8 via a resistor R1. The secondary winding N2 forms a series circuit together with the LED module 10 and the diode D1, and the tertiary winding N3 is provided to detect the state of the current flowing through the secondary winding N2. Here, in the present embodiment, the tertiary winding N3 constitutes a current detection unit.

  The smoothing capacitor C <b> 1 is connected in parallel to the LED module 10, smoothes the DC power supplied via the secondary winding N <b> 2, and outputs it to the LED module 10.

  In the first embodiment, the current flowing through the LED module 10 is input to the CS terminal of the control IC 121 and the inverting input terminal of the operational amplifier 93. However, in this embodiment, the current flowing through the primary winding N1 is used. The signal is input to the CS terminal and the inverting input terminal. That is, in this embodiment, the off timing of the switching element Q1 is determined according to the current flowing through the primary winding N1.

  Next, the basic operation of the lighting device 1 will be described. When a switch (not shown) that activates the lighting device 1 is turned on, the rectifier circuit 7 rectifies the AC voltage supplied from the commercial power supply 100 into a DC voltage, and the power factor correction circuit 8 further than the rectifier circuit 7. The output DC voltage is converted into a DC voltage having a desired voltage value.

  The clock signal generation unit 122 (signal output unit) generates a clock signal having a constant frequency (for example, 40 kHz), and outputs the generated clock signal to the determination unit 123 (second control unit). Further, the voltage signal corresponding to the state of the current flowing through the secondary winding N2 of the transformer T1 (voltage signal corresponding to the current flowing through the tertiary winding N3) is input to the determination unit 123. Then, the determination unit 123 determines whether or not one cycle of the clock signal has ended, and determines the state of the current flowing through the secondary winding N2 at the timing when one cycle of the clock signal ends.

  At this time (before starting the converter circuit 13), no current flows through the primary winding N1, the secondary winding N2, and the tertiary winding N3, and the voltage signal is not input to the determination unit 123. The determination unit 123 determines that the current flowing through the secondary winding N2 is zero, and outputs a Lo signal to the control IC 121 (first control unit). When the Lo signal from the determination unit 123 is input to the ZCD terminal, the control IC 121 outputs a Hi signal (ON signal) from the OUT terminal to the switching element Q1.

  As a result, the switching element Q1 is turned on, current flows through the primary winding N1 of the transformer T1 by the DC power output from the power factor correction circuit 8, and magnetic energy is accumulated in the core. At this time, since the diode D1 connected in series with the secondary winding N2 is in the reverse direction, no induced current flows through the secondary winding N2. When the current flowing through the primary winding N1 rises as time passes and the voltage signal corresponding to this current reaches a voltage level corresponding to the threshold value, the control IC 121 sends a Lo signal (off signal) to the switching element Q1. ) And the switching element Q1 is turned off.

  When the switching element Q1 is turned off, the magnetic energy accumulated in the core is released, and a current flows through the secondary winding N2 via the diode D1, thereby turning on the LED module 10. If the current flowing through the secondary winding N2 decreases with the passage of time and the current flowing through the secondary winding N2 becomes zero at the end of one cycle of the clock signal, the determination unit 123 determines that the control IC 121 Outputs a Lo signal. As a result, the switching element Q1 is turned on, a current flows through the primary winding N1 again, and magnetic energy is accumulated in the core.

  As described above, the LED module 10 is lit at a predetermined dimming level by repeating the on / off operation of the switching element Q1.

  According to the present embodiment, when an electronic component is in an open state or a short-circuit state due to a mounting error or aging, as in the first embodiment, the secondary winding is performed at the end of one cycle of the clock signal. The switching element Q1 is kept off until the current flowing through the line N2 becomes zero. When the current flowing through the secondary winding N2 is zero at the end of one cycle of the clock signal, the switching element Q1 is turned on. I have to. As a result, as in the first embodiment, the secondary winding of the transformer T1 can be used even when the electronic component is opened or short-circuited due to, for example, a mounting error or aging of the electronic component constituting the control circuit 12. The current flowing through the line N2 can be set to the discontinuous mode, and as a result, an excessive increase in the current flowing through the LED module 10 can be suppressed.

  In this embodiment, the transformer T1 including the primary winding N1, the secondary winding N2, and the tertiary winding N3 is used. However, if the transformer includes at least the primary winding and the secondary winding. Well, it is not limited to this embodiment.

(Embodiment 3)
An embodiment of the lighting fixture A using the lighting device 1 described in the first or second embodiment will be described with reference to FIG.

  FIG. 6A is a cross-sectional view showing an example of a lighting fixture A of the present embodiment. The lighting fixture A includes a lighting device 1, a light source unit 2, a fixture body 3, and a translucent panel 4. The lighting device 1 is provided separately from the instrument body 3.

  The instrument body 3 is formed in a rectangular box shape with an open bottom surface, and is embedded in the back of the ceiling through an embedding hole 101 a provided in the ceiling material 101. Moreover, the translucent panel 4 formed in the rectangular plate shape is attached to the opening surface of the instrument main body 3 by an appropriate method.

  The light source unit 2 includes a substrate 21 formed in a rectangular plate shape, and a plurality (three in FIG. 6A) of light emitting elements 22 mounted on the substrate 21. The instrument body 3 is housed in the lower direction. Further, the substrate 21 is electrically connected to the lighting device 1 through the electric wire 5, and lighting power is supplied from the lighting device 1.

  According to this embodiment, by using the lighting device 1 described in the first or second embodiment, it is possible to provide the lighting fixture A that suppresses an excessive increase in the current flowing through the light emitting element 22.

  FIG. 6B is a cross-sectional view illustrating another example of the lighting fixture A. In this example, the lighting device 1 described in the first or second embodiment is housed in the fixture body 3, and a heat radiating plate 61 is attached to the back surface of the substrate 21 of the light source unit 2. In addition, the structure of other than that is the same as that of the lighting fixture A shown to Fig.6 (a), attaches | subjects the same code | symbol to the same component, and abbreviate | omits description. And according to this example, the lighting fixture A which suppressed that the electric current which flows into the light emitting element 22 rises excessively can be provided by using the lighting device 1 demonstrated in the above-mentioned Embodiment 1 or 2. .

  Here, the above-described lighting fixture A can be applied to a lighting fixture with a remote control or a lighting system compatible with remote operation. In a large-scale system having a large number of remote systems and lighting fixtures, it may be difficult to grasp a failure of each lighting fixture. However, by applying the lighting fixture A described above, the light-emitting element 22 can be applied. It is possible to provide an illumination system that suppresses an excessive increase in flowing current.

12 control circuit 121 control IC (first control unit)
122 Clock signal generator (signal output unit)
123 Discriminating unit (second control unit)
Q1 Switching element N1 Primary winding (inductor)
N2 secondary winding (current detector)
T1 transformer

Claims (4)

An inductor connected in series to the light emitting element, a switching element connected in series between a series circuit of the light emitting element and the inductor and a DC power supply, and a switching element connected in parallel to the series circuit and the switching A step-down chopper circuit comprising a rectifying element connected in a direction to discharge the stored energy of the inductor to the light emitting element when the element is off;
A control circuit for turning on and off the switching element,
The control circuit includes a signal output unit that outputs a rectangular wave signal having a constant frequency, a first control unit that turns off the switching element when a current flowing through the inductor reaches a predetermined value when the switching element is turned on, and the switching A current detection unit that detects a state of a current flowing through the inductor during a period in which the element is off; and a second control that determines the on-timing of the switching element based on the detection result of the rectangular wave signal and the current detection unit And comprising
When the second control unit detects that the current flowing through the inductor has not reached zero at the end of one cycle of the rectangular wave signal, the second control unit turns on the switching element until at least the end of the next cycle. Keep it off without
The lighting device, wherein the switching element is turned on when the current detection unit detects that the current flowing through the inductor becomes zero at the end of one cycle of the rectangular wave signal. A transformer having at least a primary winding and a secondary winding, a switching element connected in series between the primary winding and a DC power source, connected in series to the secondary winding and a light emitting element And a capacitor connected in parallel to each other, and a series circuit formed with the secondary winding and the capacitor, and connected in a direction that is cut off when the switching element is on and conductive when the switching element is off. A converter circuit comprising a rectifying element;
A control circuit for turning on and off the switching element,
The control circuit includes: a signal output unit that outputs a rectangular wave signal having a constant frequency; and a first control unit that turns off the switching element when a current flowing through the primary winding reaches a predetermined value when the switching element is turned on. A current detection unit that detects a state of a current flowing through the secondary winding during a period in which the switching element is off, and an on-timing of the switching element based on the detection result of the rectangular wave signal and the current detection unit A second control unit for determining
When the second control unit detects that the current flowing through the secondary winding does not reach zero at the end of one cycle of the rectangular wave signal, the switching is performed until at least the end of the next cycle. Continue the off state without turning on the element,
The lighting device according to claim 1, wherein when the current detecting unit detects that the current flowing through the secondary winding becomes zero at the end of one cycle of the rectangular wave signal, the switching element is turned on.   3. A lighting apparatus comprising: the lighting device according to claim 1; and the light emitting element to which lighting power is supplied from the lighting device.   A lighting system comprising the lighting fixture according to claim 3.

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