JP2011036126A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply and lighting apparatus that can stably control dimming of light. <P>SOLUTION: A reference signal Vref1 that changes from the signal value equivalent to the maximum current when all lights up according to light dimming depths k1, k2, ..., k7 of a light dimming signal k to the signal value equivalent to the minimum current when the light dimming depth is the deepest and a reference signal Vref2 that changes from the signal value equivalent to the load voltage at the time of the maximum current when all lights up to the signal value equivalent to the minimum current when the light dimming depth is the deepest are prepared so that the reference signal Vref1 is selected to execute constant current control to the light-emitting diodes 19 to 21 in a current control mode in the area close to all lighting where the light dimming depth is shallow and the reference signal Vref2 is selected to execute constant voltage control to the light-emitting diodes 19 to 21 in the voltage control mode in the area where the light dimming depth is deep. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power supply system having a dimming function in a semiconductor light emitting element such as a light emitting diode.

  Recently, as a power source for a semiconductor light emitting element such as a light emitting diode, a direct current power source device using a switching means is often used, and the power amount of the light emitting diode is adjusted to these power source devices according to a dimming signal given from the outside. The thing which has the light control function to adjust is also used.

  Conventionally, as having such a dimming function, for example, as disclosed in Patent Document 1, a voltage dimming circuit for controlling an applied voltage to a light emitting diode, and a switching control for an applied voltage to the light emitting diode. There is known a device that includes a duty dimming circuit that switches between a voltage dimming circuit and a duty dimming circuit according to a dimming control signal.

JP 2003-157986 A

  However, since Patent Document 1 performs dimming control based on the pulse width, flicker is likely to occur in the light output from the light emitting diode, and what is the current limiting element for output current control for controlling the pulse width? Separately, a switching element is required in series or in parallel with the light emitting diode, which increases the number of components and decreases the circuit efficiency.

   On the other hand, since a light emitting diode exhibits a substantially constant voltage characteristic, a component or device having a current limiting element is required for stable lighting. Generally, when controlling with a power supply device using switching means, current control is not possible. Used. This current control is an important control element in the design of the lighting device because the element temperature of the light emitting diode is determined by the value of the current flowing through the light emitting diode and thus affects the life of the element.

  Dimming the light emitting diode is relatively easy as compared with conventional discharge lamp lighting devices. This is due to the fact that the load has an electrically stable characteristic and that there is little fluctuation in external factors such as temperature. However, for example, if constant current control is used in applications that require deep dimming, it can be stably lit in a region where the current of all-light lighting is large, but in order to control the detection signal and this signal in the deep dimming region Since the current reference value is a minute signal, high accuracy is required for the accuracy of the detection circuit and the comparator, and it is easily affected by noise, making stable operation difficult. Therefore, it is conceivable to increase the signal voltage for control. However, since the current detection signal is generally detected by a resistor inserted in series with the light emitting diode, the current flowing through the light emitting diode is reduced. The power consumption in the detection resistor in a large area and the treatment of the heat generated are also obstacles to product development.

  As a solution to this problem, a method of controlling the output voltage at a constant level has been proposed. For example, the voltage at which the light emitting diode is turned on is higher than that of a general silicon diode. For example, in a GaN-based diode represented by blue, a current starts to flow from about 2.5 V. It is about 5V, and even with deep dimming, relatively stable dimming can be performed without being affected by the performance of the light emitting diode or noise. However, since the forward voltage of the light emitting diode has a negative temperature characteristic, self-heating occurs when a current is passed, and the forward voltage decreases and the current further increases, so that heat generation increases and thermal runaway occurs. Concerned. Moreover, the variation of the light emitting diodes is large, and even if the output of the lighting device is adjusted, the output current varies due to individual differences of the light emitting diodes. This is the same even in the dimming state, and the current flowing through the light emitting diode varies depending on the temperature characteristics and the variation of the light emitting diode, and thus the light output of the light emitting diode varies.

  This invention is made | formed in view of the said situation, and it aims at providing the power supply device and lighting fixture which can implement | achieve stable dimming control.

  The power supply system according to claim 1, wherein a semiconductor light emitting element, a dimming operation unit that outputs a dimming signal, and a dimming signal from the dimming operation unit are input, and the semiconductor light emission is performed according to the dimming signal. Semiconductor light emission by setting a current control mode for controlling a current continuously supplied to the element or a voltage control mode for controlling a voltage applied to the semiconductor light emitting element while continuously supplying current to the semiconductor light emitting element And control means for controlling lighting of the element.

  According to the present invention, the current control mode and the voltage control mode can be easily switched only by selecting the reference signal in accordance with the dimming signal from the dimming operation unit.

The perspective view of the lighting fixture to which the power supply device concerning the 1st Embodiment of this invention is applied. Sectional drawing of the lighting fixture to which the power supply device concerning 1st Embodiment is applied. The figure which shows schematic structure of the power supply device concerning the 1st Embodiment of this invention. The figure explaining the reference signal used for 1st Embodiment. The figure which shows the load characteristic of the power supply device concerning 1st Embodiment. The figure explaining the reference signal of the power supply device concerning a 1st embodiment. The figure which shows schematic structure of the power supply device concerning the 2nd Embodiment of this invention. The figure which shows the load characteristic of the power supply device concerning 2nd Embodiment. The figure explaining the reference signal used for the 3rd Embodiment of this invention. The figure explaining the reference signal used for 3rd Embodiment. The figure explaining the other reference signal used for 3rd Embodiment. The figure which shows schematic structure of the power supply device concerning the 4th Embodiment of this invention. The figure which shows the load characteristic of the power supply device concerning 4th Embodiment. The figure which shows the VI characteristic of the light emitting diode used for 4th Embodiment. The figure explaining the variation range of the light emitting diode used for 4th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) First, a lighting fixture to which the power supply apparatus of the present invention is applied will be briefly described. 1 and 2, reference numeral 1 denotes an instrument body, and the instrument body 1 is made of aluminum die-casting and has a cylindrical shape with both ends opened. The appliance body 1 is internally divided into three in the vertical direction by partition members 1 a and 1 b, and a space between the lower opening and the partition member 1 a is formed in the light source unit 2. The light source unit 2 is provided with a plurality of LEDs 2a and reflectors 2b as semiconductor light emitting elements. The plurality of LEDs 2a are arranged and mounted at equal intervals along the circumferential direction of a disk-shaped wiring board 2c provided on the lower surface of the partition member 1a.

  A space between the partition members 1 a and 1 b of the instrument body 1 is formed in the power supply chamber 3. In the power supply chamber 3, a wiring board 3a is disposed on the partition member 1a. The wiring board 3a is provided with each electronic component constituting the power supply device of the present invention for driving the plurality of LEDs 2a. The DC power supply device and the plurality of LEDs 2 a are connected by lead wires 4.

  A space between the partition plate 1 b of the instrument body 1 and the upper opening is formed in the power supply terminal chamber 5. In the power terminal room 5, a power terminal block 6 is provided on the partition plate 1b. This power supply terminal block 6 is a terminal block for supplying AC power of commercial power to the power supply device in the power supply chamber 3, and serves as a power cable terminal portion on both sides of the box 6a made of electrically insulating synthetic resin. It has an insertion port 6b, an insertion port 6c serving as a feed cable terminal, a release button 6d for separating the power line and the feed line, and the like.

  FIG. 3 shows a schematic configuration of the power supply device according to the first embodiment of the present invention incorporated in the power supply chamber 3 of the lighting fixture configured as described above.

  In FIG. 3, 11 is an AC power source, and this AC power source 11 is a commercial power source (not shown). The AC power supply 11 is connected to an input terminal of a full-wave rectifier circuit 12. The full wave rectification circuit 12 generates an output obtained by full wave rectification of the AC power from the AC power supply 11.

  A ripple current smoothing capacitor 13 is connected between the positive and negative output terminals of the full-wave rectifier circuit 12. Further, a series circuit of a primary winding 14a of a switching transformer 14 which is a flyback transformer and a switching transistor 15 as a switching means is connected to both ends of the capacitor 13. The switching transformer 14 has a secondary winding 14b magnetically coupled to the primary winding 14a.

  Connected to the secondary winding 14b of the switching transformer 14 is a rectifying / smoothing circuit 18 comprising a diode 16 and a smoothing capacitor 17 having polarities as shown in FIG. The rectifying / smoothing circuit 18 constitutes a DC output generating means together with the switching transistor 15 and the switching transformer 14, rectifies the AC output generated from the secondary winding 14b of the switching transformer 14 by the diode 16, and the rectified output is smoothed by the smoothing capacitor. 17 is smoothed and generated as a DC output.

  At both ends of the smoothing capacitor 17 of the rectifying and smoothing circuit 18, a plurality of (three in the illustrated example) semiconductor light emitting elements connected in series as loads are equivalent to the light emitting diodes 19 to 21 (LED 2a described in FIG. 2). .) Is connected.

  A current detection circuit 22 is connected in series to the series circuit of the light emitting diodes 19 to 21. The current detection circuit 22 includes a resistor 221 that is an impedance element, detects a current flowing through the light emitting diodes 19 to 21, and outputs the current detection value I as a detection signal. A load voltage detection circuit 23 is connected in parallel to the series circuit of the light emitting diodes 19 to 21. The load voltage detection circuit 23 is composed of a series circuit of resistors 231 and 232 which are impedance elements, detects the load voltage applied to the light emitting diodes 19 to 21, and outputs the load voltage V as a detection signal. .

  A dimming control unit 33 is connected to the current detection circuit 22 and the load voltage detection circuit 23 as dimming control means. The dimming control unit 33 includes comparators 34 and 35 and a reference signal output unit 36. The comparator 34 outputs a comparison result between the detection signal (current detection value I) of the current detection circuit 22 and the reference signal Vref1 of the reference signal output unit 36. The comparator 35 outputs a comparison result between the detection signal (load voltage V) of the load voltage detection circuit 23 and the reference signal Vref2 of the reference signal output unit 36. A control circuit 30 is connected to the comparators 34 and 35 via diodes 37 and 38, respectively.

  The reference signal output unit 36 corresponds to the dimming depths k1 to k7 based on the dimming signal k of the dimming operation unit 39 (here, the dimming depth k1 is the shallowest and deeper toward the dimming depth k7). The reference signal Vref1 and the reference signal Vref2 as shown in FIG. In this case, the reference signal Vref1 changes from a signal value corresponding to the maximum current during all light to a signal value corresponding to the minimum current when the dimming depth is the deepest. The reference signal Vref2 changes from a signal value corresponding to the load voltage at the maximum current during all light to a signal value corresponding to the minimum current when the dimming depth is the deepest. In this case, the reference signal Vref2 does not become zero because the on-voltage of the light emitting diode remains even at the time of transition to the extinguished state where no current flows. That is, in this case, as shown in FIG. 6, a current control range B and a voltage control range C are obtained for the VI characteristic A of the light emitting diode.

  The control circuit 30 controls the on / off operation of the switching transistor 15 by the outputs of the comparators 34 and 35 according to the reference signals Vref1 and Vref2, and controls the output supplied to the light emitting diodes 19 to 21 from the rectifying and smoothing circuit 18. Thereby, as a power supply device, as shown in FIG. 5, different load characteristics can be obtained according to the dimming depths k1, k2,... K7 of the dimming signal k. In this case, the load characteristics corresponding to the dimming depths k1, k2,..., K7 are such that the current If is constant with respect to the change in the voltage Vf, and the voltage Vf is constant when the voltage Vf reaches a predetermined voltage. In addition, the load characteristics corresponding to the light control depths k1, k2,... K7 are set in the relationship with the VI characteristics A of the light emitting diodes 19 to 21 as shown in FIG. In this case, the operating points a1 to a4 at the intersections of the load characteristics corresponding to the dimming depths k1 to k4 and the VI characteristics A are current mode control, and the load characteristics and the VI characteristics corresponding to the dimming depth k5. The operating point a5 at the intersection with A is a critical point, and the operating points a6 and a7 at the intersection between the load characteristic corresponding to the dimming depths k6 and k7 and the VI characteristic A are voltage mode control.

  In such a configuration, first, when the dimming signal k of all the lights (for example, the dimming depth k1) is output from the dimming operation unit 31, the dimming depth k1 shown in FIG. 5 according to the dimming signal k. Can be obtained. In this case, the intersection of the load characteristic corresponding to the light control depth k1 and the VI characteristic A of the light emitting diodes 19 to 21 is the operating point a1 of the light emitting diodes 19 to 21. Further, as shown in FIG. 4, the reference signal output unit 36 sets Vra1 as the reference signal Vref1 and Vrb1 as the reference signal Vref2 based on the light control depth k1.

  As a result, the comparison result of the detection signal (current detection value I) of the current detection circuit 22 and the reference signal Vra1 of the reference signal output unit 36 is output from the comparator 34, and the detection signal (the detection signal of the load voltage detection circuit 23 ( The comparison result between the load voltage V) and the reference signal Vrb1 of the reference signal output unit 36 is output. In this case, since the reference signal has a relationship of Vra1> Vrb1, the output of the comparator 34 has priority and the control circuit 30 Given to. As a result, the on / off operation of the switching transistor 15 is controlled so that the current flowing through the light emitting diodes 19 to 21 is constant based on the detection signal (current detection value I) of the current detection circuit 22.

  Next, when a dimming signal k having a dimming depth k5 is output by operating the dimming operation unit 31, for example, load characteristics corresponding to the dimming depth k5 shown in FIG. 5 are obtained. In this case, the intersection of the load characteristic corresponding to the light control depth k5 and the VI characteristic A of the light emitting diodes 19 to 21 is the operating point a5 of the light emitting diodes 19 to 21. Further, as shown in FIG. 4, the reference signal output unit 36 sets Vra5 as the reference signal Vref1 and Vrb5 as the reference signal Vref2 by setting the dimming depth k5.

  Also in this case, a comparison result between the detection signal (current detection value I) of the current detection circuit 22 and the reference signal Vra5 of the reference signal output unit 36 is output from the comparator 34, and the load voltage detection circuit 23 is output from the comparator 35. The comparison result between the detection signal (load voltage V) and the reference signal Vrb5 of the reference signal output unit 36 is output. The reference signal here has a relationship of Vra5 = Vrb5, and the comparator 34 and the comparator 35 Outputs are equal. Thus, the control circuit 30 controls the on / off operation of the switching transistor 15 based on both the detection signal (current detection value I) of the current detection circuit 22 and the detection signal (load voltage V) of the load voltage detection circuit 23.

  Next, for example, when a dimming signal k having a dimming depth k6 is output from the dimming operation unit 31, a load characteristic corresponding to the dimming depth k6 illustrated in FIG. 5 is obtained. In this case, the intersection of the load characteristic corresponding to the light control depth k6 and the VI characteristic A of the light emitting diodes 19 to 21 is the operating point a6 of the light emitting diodes 19 to 21. Further, as shown in FIG. 4, the reference signal output unit 36 sets Vra6 as the reference signal Vref1 and Vrb6 as the reference signal Vref2 by setting the dimming depth k6.

  As a result, a comparison result between the detection signal (current detection value I) of the current detection circuit 22 and the reference signal Vra6 of the reference signal output unit 36 is output from the comparator 34, and the load voltage detection circuit 23 of the load voltage detection circuit 23 is output from the comparator 35. A comparison result between the detection signal (load voltage V) and the reference signal Vrb6 of the reference signal output unit 36 is output. In this case, since the reference signal has a relationship of Vrb1> Vra1, the output of the comparator 35 has priority. To the control circuit 30. As a result, the on / off operation of the switching transistor 15 is controlled so that the load voltage of the light emitting diodes 19 to 21 is constant based on the detection signal (load voltage V) of the load voltage detection circuit 23.

  Therefore, in this way, it corresponds to the minimum current when the dimming depth is deepest from the signal value corresponding to the maximum current at the time of all lights according to the dimming depths k1, k2,... K7 of the dimming signal k. A reference signal Vref1 that changes to a signal value, a reference signal Vref2 that changes from a signal value corresponding to a load voltage at the maximum current during all light to a signal value corresponding to a minimum current when the dimming depth is the deepest, are prepared, In the region where the light control depth is close to all light, the reference signal Vref1 is selected and constant current control is performed on the light emitting diodes 19 to 21 in the current control mode. In the region where the light control depth is deep, the reference signal Vref2 is selected and voltage control is performed. The light emitting diodes 19 to 21 were controlled at a constant voltage depending on the mode. In this way, constant current control and constant voltage control can be smoothly switched in accordance with the dimming depths k1, k2,... K7 of the dimming signal k, so that a wide range from a shallow region to a deep region can be obtained. Dimming control of the range can be performed stably. Further, since pulse width control is not used for dimming control, flicker can be prevented from occurring in the light output of the light-emitting diode, compared with the case where dimming control is performed by the pulse width of Patent Document 1, and By eliminating the need for switch elements for dimming control, the circuit configuration can be simplified, the number of parts can be reduced, the size and cost of the device can be reduced, and the reduction in circuit efficiency is also suppressed. can do.

  (Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 7 shows a schematic configuration of a power supply device according to the second embodiment of the present invention, and the same parts as those in FIG.

  In this case, a dimming control unit 41 is connected to the current detection circuit 22 and the load voltage detection circuit 23 as dimming control means. In the dimming control unit 41, the positive input terminal of the first operational amplifier 42 is connected to the current detection circuit 22. The first operational amplifier 42 has a negative input terminal grounded via a resistor 43 and is connected to an output terminal via a resistor 44. The output terminal of the first operational amplifier 42 is connected to one input terminal of the comparator 46 via the diode 45. Further, the positive input terminal of the second operational amplifier 47 is connected to the load voltage detection circuit 23. The second operational amplifier 47 has a negative input terminal connected to the output terminal, is connected to one input terminal of the comparator 46 via a diode 48, and is further connected to a positive input of the third operational amplifier 50 via a resistor 49. The terminal is connected. The third operational amplifier 50 has a positive input terminal connected to a connection point of a series circuit of resistors 51 and 52 connected between the output terminal of the first operational amplifier 42 and the ground, and a negative input terminal connected to the ground. Has been. Further, the third operational amplifier 50 has an output terminal connected to one input terminal of the comparator 46 via a diode 53. The comparator 46 receives the dimming signal k from the dimming operation unit 39 at the other input terminal, and inputs the comparison result of the signals supplied to these input terminals to the control circuit 30.

  In such a configuration, when a dimming signal k is input from the dimming operation unit 31, load characteristics as shown in FIG. 8 are obtained according to the dimming depths k1 to k5 at this time. In this case, the relationship between the load characteristics corresponding to the light control depths k1, k2,... K5 and the VI characteristics A of the light emitting diodes 19 to 21 is as shown in FIG.

  First, when a dimming signal k of all light (for example, dimming depth k1) is input by operating the dimming operation unit 31, a load corresponding to the dimming depth k1 shown in FIG. Characteristics are obtained. In this case, the intersection of the load characteristic corresponding to the dimming depth k1 and the VI characteristic A of the light emitting diodes 19 to 21 is the operating point a1 of the light emitting diodes 19 to 21, and at this operating point a1, the current detection circuit 22 The output of the first operational amplifier 42 corresponding to the detection signal (current detection value I) is input to the comparator 46, and the light emitting diodes 19 to 21 are subjected to constant current control.

  Next, when a dimming signal k having a dimming depth k5 is input from the dimming operation unit 31, load characteristics corresponding to the dimming depth k5 in FIG. 8 are obtained according to the dimming signal k. In this case, the intersection of the load characteristic corresponding to the dimming depth k5 and the VI characteristic A of the light emitting diodes 19 to 21 becomes the operating point a5 of the light emitting diodes 19 to 21, and at this operating point a5, the load voltage detection circuit 23 The output of the second operational amplifier 47 corresponding to the detection signal (load voltage V) is input to the comparator 46, and the light emitting diodes 19 to 21 are controlled at a constant voltage by the control circuit 30.

  Next, when a dimming signal k having a dimming depth k3 is input from the dimming operation unit 31, an output of a load characteristic corresponding to the dimming depth k3 in FIG. 8 is obtained according to the dimming signal k. In this case, the intersection of the load characteristic corresponding to the dimming depth k3 and the VI characteristic A of the light emitting diodes 19 to 21 is the operating point a3 of the light emitting diodes 19 to 21, and the current detection circuit 22 detects the operating point a3. The output of the third operational amplifier 50 corresponding to the signal (current detection value I) and the detection signal (load voltage V) of the load voltage detection circuit 23 is input to the comparator 46, and the light emitting diodes 19 to 21 are controlled by the control circuit 30. Power controlled.

  Therefore, in this way, when the operating point of the light emitting diodes 19 to 21 is located between the current control mode and the voltage control mode, the detection signal (current detection value I) of the current detection circuit 22 and the load voltage Since the power of the light emitting diodes 19 to 21 is controlled by the output of the third operational amplifier 50 according to the detection signal (load voltage V) of the detection circuit 23, the control shifts between the current control mode and the voltage control mode. It can be performed more smoothly.

  (Third Embodiment) Next, a third embodiment will be described. In this case, FIG. 3 is used as a schematic configuration of the power supply device according to the third embodiment.

  Incidentally, in the first embodiment, the reference signal output unit 36 outputs the reference signal Vref1 and the reference signal Vref2 separately. However, in the third embodiment, the reference signal Vref1 and the reference signal Vref2 are combined into one reference signal. The signal Vref is output. As shown in FIG. 9A, the reference signal Vref generates a first signal generator 55 that generates a reference signal Vref1 used in the current control mode region and a reference signal Vref2 used in the voltage control mode region. The second signal generator 56 is provided, and the reference signals Vref1 and Vref2 of the first and second signal generators 55 and 56 are output through the diodes 57 and 58, respectively, so that FIG. The reference signal Vref shown in FIG. In this case, as shown in FIG. 10A, the reference signal Vref1 changes from a signal value corresponding to the maximum current during all light to a signal value corresponding to the minimum current when the dimming depth is deepest. Further, the reference signal Vref2 in the voltage control mode region corresponds to the minimum current when the dimming depth is the deepest from the signal value corresponding to the load voltage at the maximum current at the time of all light as shown in FIG. 10 (b). However, the reference voltage Vref2 does not become zero because the ON voltage of the light emitting diode on the equivalent circuit remains even at the time of transition to the extinguished state where no current flows at all. Then, as shown in FIG. 9B, the reference signal Vref is generated in each region of the current control mode and the voltage control mode by giving priority to the larger signal among the reference signals Vref1 and Vref2, and this reference signal Vref is generated. A reference signal for the comparators 34 and 35 is used.

  Even if it does in this way, the effect similar to 1st Embodiment can be acquired.

  (Modification) In the above description, the reference signal Vref is generated by giving priority to a larger signal among the reference signals Vref1 and Vref2. However, the current control mode and the voltage control mode may not be switched smoothly. Therefore, as shown in FIG. 11A, in addition to the first signal generator 55 and the second signal generator 56, a reference signal Vref3 having an intermediate gain between the reference signal Vref1 and the reference signal Vref2 is generated. 11 is provided, and the reference signals Vref1, Vref2, and Vref3 of the first to third signal generators 55 and 56 are output through the diodes 57, 58, and 60, respectively, as shown in FIG. The reference signal Vref shown in b) is output. In this way, by interposing the reference signal Vref3 that changes between the gains of the reference signal Vrefa and the reference signal Vrefb between the regions of the current control mode and the voltage control mode, the current control mode and the voltage control It is possible to smoothly shift the control mode between the mode areas.

  (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. FIG. 12 shows a schematic configuration of a power supply apparatus according to the fourth embodiment of the present invention, and the same parts as those in FIG.

  In this case, a dimming control unit 24 is connected to the current detection circuit 22 and the load voltage detection circuit 23 as dimming control means. The dimming control unit 24 includes a multiplier 26, an adder 27, and a comparator 28. The multiplier 26 outputs a signal obtained by multiplying the detection signal (load voltage V) of the load voltage detection circuit 23 by the dimming signal k of the dimming operation unit 31. The adder 27 generates an output a obtained by adding the output of the multiplier 26 and the detection signal (current detection value I) of the current detection circuit 22. The comparator 28 outputs a comparison result between the output a of the adder 27 and the reference value (constant) 29.

  The comparator 28 is connected to a control circuit 30 that constitutes a control means together with the dimming control unit 24. The control circuit 30 is driven by a power supply unit (not shown). By the operation, the switching transistor 15 is turned on and off, the switching transformer 14 is switched and output supplied from the rectifying and smoothing circuit 18 to the light emitting diodes 19 to 21. To control. In this case, the control circuit 30 is based on the output of the comparator 28 of the dimming control unit 24, that is, the product of the detection signal (load voltage V) of the load voltage detection circuit 23 and the dimming signal k, and the current detection circuit 22. Based on the value a obtained from the sum of the detection signals (current detection value I), the output supplied to the light emitting diodes 19 to 21 is controlled so that the value a is always constant.

  The dimming operation unit 31 outputs, for example, a dimming signal k having different dimming depths by changing the duty ratio of the pulse signal. Here, the dimming depths k1, k2,... K7 (dimming depth k1) Is the shallowest, and the light control signal k is deeper toward the light control depth k7.

  Thereby, as a power supply device, as shown in FIG. 13, different load characteristics can be obtained according to the dimming depths k1, k2,... K7 of the dimming signal k. In this case, the respective load characteristics corresponding to the light control depths k1, k2,... K7 are radially centered on a constant value a (position of load impedance 0) on the current axis, and If = a−k (Vf). Expressed by a linear function. Thereby, If + k (Vf) = a (1), that is, the relationship between the current detection value I of the current detection circuit 22 and the product of the dimming signal k and the load voltage V is always a constant value a. can get.

  Next, the operation of the embodiment configured as described above will be described.

  In this case, it is assumed that the load characteristics corresponding to the dimming depths k1, k2,... K7 and the VI characteristics A of the light emitting diodes 19 to 21 have the relationship shown in FIG.

  First, when the dimming signal k of all the lights (for example, the dimming depth k1) is output from the dimming operation unit 31, the load characteristics corresponding to the dimming depth k1 shown in FIG. 13 according to the dimming signal k. Is obtained. In this case, the intersection of the load characteristic corresponding to the light control depth k1 and the VI characteristic A of the light emitting diodes 19 to 21 is the operating point a11 of the light emitting diodes 19 to 21.

  In this state, when the switching transistor 15 is turned on and off by the control circuit 30, the switching transformer 14 is driven to be switched. When the switching transistor 15 is turned on, a current is passed through the primary winding 14a of the switching transformer 14 to accumulate energy. With 15 off, the energy stored in the primary winding 14a is released through the secondary winding 14b. As a result, a direct current output is generated via the rectifying and smoothing circuit 18, and the light emitting diodes 19 to 21 are turned on by this direct current output.

  In this case, the detection signal (load voltage V) of the load voltage detection circuit 23 and the dimming signal k are multiplied by the multiplier 26, and the output of the multiplier 26 and the detection signal (current detection value I) of the current detection circuit 22 are multiplied. An adder 27 adds to generate an output a, and a comparison result between the output a and a reference value (constant) 29 is output from a comparator 28. Based on this output, the output a is always a constant value. The output supplied to the light emitting diodes 19 to 21 is controlled by the control circuit 30.

  In this case, at the operating point a11 shown in FIG. 13, the k (Vf) component that determines a in the above equation (1) is substantially zero, and only the If component (see (a0-a) in FIG. 13). . As a result, the light emitting diodes 19 to 21 are controlled to be lit while the current control mode is emphasized.

  Next, for example, when a dimming signal k corresponding to the dimming depth k2 is output from the dimming operation unit 31, a load corresponding to the dimming depth k2 illustrated in FIG. 13 according to the dimming signal k at this time. Characteristics are obtained. Thereby, the intersection of the load characteristic corresponding to the light control depth k2 and the VI characteristic A of the light emitting diodes 19 to 21 becomes the operating point a12.

  In this case as well, the light emitting diodes 19 to 21 are turned on by turning on and off the switching transistor 15 by the control circuit 30 as described above. However, at the operating point a12 shown in FIG. The k (Vf) component is (a-a1) shown in FIG. 13 and the If component is (a0-a1) shown in FIG. 13. In this case as well, the If component occupies most of the light emitting diodes 19-21. The current control mode is emphasized and lighting control is performed.

  Thereafter, when a dimming signal k corresponding to the dimming depth k6 is output from the dimming operation unit 31, a dimming depth k6 shown in FIG. Corresponding load characteristics are obtained. Thereby, the intersection of the load characteristic corresponding to the light control depth k6 and the VI characteristic A of the light emitting diodes 19-21 becomes the operating point a16.

  In this case as well, the light emitting diodes 19 to 21 are turned on by turning on and off the switching transistor 15 by the control circuit 30 as described above. However, at the operating point a16 shown in FIG. The k (Vf) component is (a-a6) shown in FIG. 13, and the If component is (a0-a6) shown in FIG. In this state, the If component is small, and a is determined by the k (Vf) component that occupies most, and the light emitting diodes 19 to 21 are controlled to be lit with the voltage control mode emphasized.

  Although only the operating points a11, a12, and a16 have been described here, the same applies to the other operating points a13 to a15, a17.

  Therefore, in this way, when the dimming depth is adjusted in the range of k1, k2,... K7 by the dimming signal k, the dimming depth is shallow due to the load characteristics according to these dimming depths k1, k2,. In a region close to all light, the light emitting diodes 19 to 21 are controlled to be turned on in the current control mode, and the light emitting diodes 19 to 21 are turned on by gradually shifting from the current control mode to the voltage control mode as the dimming depth increases. I tried to control it. As a result, the dimming control method can be smoothly shifted in accordance with the dimming depth of the dimming signal in accordance with the current control mode and the voltage control mode, and a wide range from a shallow region to a deep region can be obtained. Dimming control can be performed stably. Further, since pulse width control is not used for dimming control, flicker can be prevented from occurring in the light output of the light-emitting diode, compared with the case where dimming control is performed by the pulse width of Patent Document 1, and By eliminating the need for switch elements for dimming control, the circuit configuration can be simplified, the number of parts can be reduced, the size and cost of the device can be reduced, and the reduction in circuit efficiency is also suppressed. can do.

  Further, the VI characteristics of the light emitting diodes 19 to 21 have a region that rises exponentially as shown in FIG. 14, and Amax and Amax centered on Acen due to variations in elements and variations in operating points due to temperature characteristics. It is known to vary between Amin. In this case, since the current control mode is selected in the region where the light control depth is shallow and a relatively large current flows, the variation B11 in the region where ΔI / ΔV is small as shown in FIG. On the other hand, the variation B12 in the region where ΔI / ΔV is large can be reduced. Further, in the region where the light control depth is deep and the small current flows, the voltage control mode is selected as described above. Therefore, as shown in FIG. 15B, ΔI / ΔV with respect to the variation B21 in the region where ΔI / ΔV is large. The variation B22 in the region where ΔV is small can be reduced. Thereby, the fluctuation | variation of the optical output resulting from the dispersion | variation in the light emitting diodes 19-21 and the dispersion | variation in the operating point by a temperature characteristic can be suppressed as much as possible.

In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not change the summary. For example, in the above-described embodiment, an example of an analog circuit has been described. However, a control method using a microcomputer or digital processing may be employed. In addition, the dimming depth switching includes continuously dimming and stepwise dimming, and may be phase control in which the effective voltage to the load is varied by controlling the conduction period of the power supply voltage. . Further, the dimming signal can be a dedicated signal line or a power line signal in which the dimming signal is superimposed on the power supply wire.
Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and is described in the column of the effect of the invention. If the above effect is obtained, a configuration in which this configuration requirement is deleted can be extracted as an invention.

  DESCRIPTION OF SYMBOLS 1 ... Instrument body, 2 ... Light source part, 3 ... Power supply room, 6 ... Power supply terminal block, 11 ... AC power supply, 12 ... Full wave rectification circuit, 14 ... Switching transformer, 15 ... Switching transistor, 18 ... Rectification smoothing circuit, 19 21 to LED, 22 to current detection circuit, 23 to load voltage detection circuit, 24 to dimming control unit, 26 to multiplier, 27 to adder, 28 to comparator, 29 to reference value, 30 to control circuit 31 ... Dimming operation unit, 33 ... Dimming control unit, 34.35 ... Comparator, 36 ... Reference signal output unit, 39 ... Dimming operation unit, 41 ... Dimming control unit, 55 ... First signal generation 56 ... second signal generator 59 ... third signal generator

Claims (1)

A semiconductor light emitting device;
A dimming operation unit for outputting a dimming signal;
A dimming signal from the dimming operation unit is input, and a current control mode for controlling a current continuously supplied to the semiconductor light emitting element according to the dimming signal or a current is continuously supplied to the semiconductor light emitting element While controlling the lighting of the semiconductor light emitting element by setting a voltage control mode for controlling the voltage applied to the semiconductor light emitting element;
A power supply system comprising:

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