JP2013125730A - Led power supply device, and illuminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED power supply device capable of suppressing variation in power consumption of an LED load, and to provide an illuminating device having this LED power supply device.SOLUTION: An LED power supply device 1 has: a DC output generation circuit 2 outputting a DC voltage depending on an on-off operation of a switching element Q1; an LED load 3 connected between outputs of the DC output generation circuit 2; and control means 5 performing control so that an output of the DC output generation circuit 2 satisfies a control formula by on-off controlling the switching element Q1 depending on a total value of a detection voltage value of a load voltage of the LED load 3 and a detection current value of a load current of the LED load 3. The control formula is represented as output voltage=-a*output current+constant. Here, a is set to a value larger than a value obtained by dividing the load voltage of the LED load 3 in full lighting by a double of the load current.

Description

  Embodiments described herein relate generally to an LED power supply device that lights an LED load in response to a dimming signal, and an illumination device that includes the LED power supply device.

  As a power source for an LED load, a direct current power source device using a switching means is often used. Some of the power supply devices have a dimming function for adjusting the light amount of the LED load in accordance with an external dimming signal.

  The present applicant has proposed a power supply device capable of realizing stable dimming control in a wide dimming range from a shallow region to a deep region of the LED load (see Patent Document 1). The power supply device of Patent Document 1 has a characteristic that intersects the voltage-current characteristic of the LED load, and has an output impedance provided so that the intersection is an operating point of the LED load. And a power supply device has the advantage that it can suppress the dispersion | variation in the electric current which flows into LED load with respect to the dispersion | variation by the individual difference and temperature characteristic of LED load, and can suppress the dispersion | variation in the light output of LED load. ing.

Japanese Patent Laying-Open No. 2009-231147 (page 5-6, FIG. 4)

  Considering the case where the variation of the LED load is large, depending on the setting of the load characteristic of the output impedance, the crossing angle with the voltage-current characteristic of the LED load may be small, especially in the region where the dimming depth is shallow. In this case, the variation in the power consumption of the LED load with respect to the variation due to individual differences in the LED load may increase.

  An object of the present embodiment is to provide an LED power supply device that can suppress variation in power consumption of an LED load and an illumination device including the LED power supply device.

  The LED power supply device according to the present embodiment includes a DC output generation circuit, an LED load, and control means.

  The direct current output generation circuit includes a switching element that is on / off controlled by a control unit. And it forms so that the DC voltage according to the ON / OFF operation | movement of a switching element may be output. The LED load is connected between the outputs of the DC output generation circuit.

  The control means controls on / off of the switching element of the DC output generation circuit according to the total value of the detected voltage value of the load voltage applied to the LED load and the detected current value of the load current flowing through the LED load, thereby generating the DC output. The output of the circuit is controlled so as to satisfy the following expression 1.

  Formula 1; Output voltage = −a * Output current + Constant

  However, except when the detection voltage value of the load voltage is zero, a> a1 * 0.5, where a1 is a load current that flows to the LED load as a load voltage applied to the LED load at the time of all light The value divided by.

  According to the embodiment of the present invention, the control unit performs on / off control of the switching element of the DC output generation circuit according to the total value of the detected voltage value of the load voltage of the LED load and the detected current value of the load current, thereby Since the output voltage of the output generation circuit is controlled so as to satisfy −a * output current + constant, the crossing angle between the current-power characteristic of the LED power supply device and the current-power characteristic of the LED load becomes large. It can be expected that the variation range of the load power of the LED load can be suppressed with respect to the variation of the LED load.

It is a circuit diagram of the LED power supply device which shows the 1st Embodiment of this invention. Similarly, it is a characteristic diagram which shows the change of the voltage with respect to the electric current of a LED power supply device. Similarly, it is a characteristic diagram which shows the change of the electric power with respect to the electric current of a LED power supply device. It is a schematic sectional side view of the illuminating device which shows the 2nd Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the first embodiment will be described.

  The LED power supply device 1 according to this embodiment includes a DC output generation circuit 2, an LED load 3, a reference value output circuit 4, and a control means 5.

  The DC output generation circuit 2 includes an AC-DC conversion circuit 6 that converts an AC voltage into a DC voltage, and a DC-DC conversion circuit 7 that adjusts the DC voltage to a predetermined output voltage. The AC-DC conversion circuit 6 includes a rectifier 8 and a smoothing capacitor C1. The input terminal of the rectifier 8 is connected to the commercial AC power supply Vs, and the smoothing capacitor C1 is connected between the output terminals of the rectifier 8. Yes. A DC voltage obtained by rectifying and smoothing the AC voltage of the commercial AC power supply Vs is generated between both ends of the smoothing capacitor C1.

  The DC-DC conversion circuit 7 includes a series circuit of a field effect transistor Q1 and a diode D1 as a switching element connected between both ends of a smoothing capacitor C1, and a series of an inductor L1 and a capacitor C2 connected in parallel to the diode D1. And a circuit. The field effect transistor Q1 is on / off controlled by a control circuit 12 to be described later, and its on period is changed. The negative electrode side of the capacitor C2 is connected to the ground E.

  The capacitor C2 is charged by the voltage across the smoothing capacitor C1 when the field effect transistor Q1 is on, and when the field effect transistor Q1 is off, the current due to the electromagnetic energy of the inductor L1 is the inductor L1. , Flows into the closed circuit of the capacitor C2 and the diode D1, and is charged. A DC voltage corresponding to the on / off operation of the field effect transistor Q1 is generated between both ends of the capacitor C2. The voltage across the capacitor C <b> 2 is the output voltage of the DC output generation circuit 2.

  The LED load 3 has a plurality of LED elements 9 connected in series. The LED element 9 is an existing product that emits visible light such as white light. The LED load 3 is connected between both ends of the capacitor C2, which is between the outputs of the DC output generation circuit 2. A DC voltage output from the DC output generation circuit 2 is applied to the LED load 3, and a current corresponding to the DC voltage flows. Thereby, the LED element 9 is turned on and visible light is emitted. Then, the LED element 9 is dimmed according to the DC voltage output from the DC output generation circuit 2.

  And between the both ends of LED load 3, the series circuit of resistance R1 and resistance R2 which detects the voltage (load voltage) between the both ends of LED load 3 is connected. A resistor R3 for detecting a current (load current) flowing through the LED load 3 is connected between the series circuit and the negative electrode side of the capacitor C2. The load current is converted into a voltage by the resistor R3.

  The reference value output circuit 4 is connected to an external light control device 10 and receives a light control signal for changing the light control depth of the LED load 3 from the light control device 10. The dimming signal is, for example, a PWM control signal. That is, the dimming device 10 outputs dimming signals having different dimming depths by changing the duty ratio of the PWM control signal, and here, dimming signals having dimming depths k1, k2,. It is formed as follows. The reference value output circuit 4 is configured to output a reference value Vref / k corresponding to the light control depths k1, k2,..., K7. The dimming signal may be a signal that continuously changes the dimming depth.

  The control means 5 includes a comparator 11 and a control circuit 12. The comparator 11 has one input terminal connected to the reference value output circuit 4 and the other input terminal connected to the middle point s1 of the resistor R1 and the resistor R2. That is, in the comparator 11, the reference value Vref / k output from the reference value output circuit 4 is input to one input terminal, and the detected voltage value of the load voltage applied to the LED load 3 and the LED are input to the other input terminal. The total value of the detected current values of the load current flowing through the load 3 is input. Then, the comparator 11 outputs the difference between the reference value Vref / k and the total value to the control circuit 12.

  The control circuit 12 controls the field effect transistor Q1 of the DC output generation circuit 2 so that the difference output from the comparator 11 becomes zero, that is, the total value becomes the reference value Vref / k. It is formed to do. Therefore, the LED load 3 is dimmed and lit so that the dimming depths k1, k2,..., K7 of the dimming signal output from the dimming device 10 are obtained.

  The detection circuit (R1 to R3) of the LED load 3 and the control circuit 12 perform on / off control of the field effect transistor Q1 so that the output voltage and output current of the DC output generation circuit 2 satisfy the following control expression 1. Is formed. The output voltage is a load voltage (Vf) applied to the LED load 3, and the output current is a load current (If) flowing through the LED load 3.

  Equation 1; output voltage = −a * output current + constant (b)

  Here, the constant a and the constant (b) are set as follows.

  The control circuit 12 is a reference in which the total value of the detected voltage value of the load voltage (Vf) applied to the LED load 3 and the detected current value of the load current (If) flowing through the LED load 3 is output from the reference value output circuit 4. Since control is performed so as to have the value Vref / k, the following formulas 2 to 4 are obtained. The current is expressed in amperes (A), the voltage is expressed in volts (V), and the resistance is expressed in ohms (Ω).

  Formula 2; If * R3 + Vf * R2 / (R1 + R2) = Vref / k

  Formula 3; If * R3 * (R1 + R2) / R2 + Vf = Vref / k * (R1 + R2) / R2

  Formula 4; Vf = −If * R3 * (R1 + R2) / R2 + Vref / k * (R1 + R2) / R2

  As a result, the constant a is set to R3 * (R1 + R2) / R2, and the constant (b) is set to Vref / k * (R1 + R2) / R2.

  In the present embodiment, the constant a is twice the load voltage If applied to the LED load 3 when the LED load 3 is in full light, and twice the load current If flowing through the LED load 3 when the LED load 3 is in full light. The resistance values of the resistors R1 to R3 are set so as to be larger than the value divided by (Vf / (If * 2)).

  As shown in FIG. 2, the LED power supply device 1 has a voltage (Vf) characteristic (If−) with respect to a different current (If) according to the dimming depths k1, k2,. Vf characteristic) is obtained. Each of the If-Vf characteristics corresponding to the dimming depths k1, k2,..., K7 has a slope of the constant a, and the contacts b1, b2,. The constant (b) is changed according to k7.

  The intersection Z1a between the respective If-Vf characteristics corresponding to the dimming depths k1, k2,..., K7 and the If-Vf characteristics of the LED load 3 is an operating point of the LED load 3. Further, the LED load 3 changes its If-Vf characteristic due to individual differences and variations due to temperature characteristics, for example, changes as indicated by Lb and Lc in FIG. 2, and the If-Vf characteristic of the LED power supply device 1. The intersection changes as indicated by Z1b and Z1c in FIG. That is, the operating point of the LED load 3 changes on the respective If-Vf characteristics corresponding to the dimming depths k1, k2,..., K7 due to individual differences of the LED loads 3 and temperature characteristics.

And the LED load 3 consumes electric power (P) when an electric current flows and it lights. Power (P) is
Formula 5; P = Vf * If
Therefore, from Equation 1,

  Formula 6; P = −a * If ^ 2 + b * If

And appears as a convex quadratic curve (parabola). This is because as the LED load 3 is operated at an operating point farther from the vertex of the quadratic curve, power fluctuations due to individual differences in the LED load 3 and variations due to temperature characteristics increase, and when the LED load 3 is operated near the vertex of the quadratic curve. It shows that the power fluctuation with respect to the variation of the LED load 3 can be suppressed. The current value at the apex of the quadratic curve has the relationship of Equation 7 obtained by differentiating Equation 6 with current.
Formula 7; -2a * If + b = 0

And when the conditions which become the vertex of Formula 6 with the load current If1 and load voltage Vf1 at the time of all the lights of LED load 3 are calculated | required using Formula 7 and Formula 1, it will become as follows.
Formula 8; -2a * If1 + b = 0
Formula 9; Vf1 = −a * If1 + b

Formula 10; 2a * If1 = a * If1 + Vf1
Formula 11; a = Vf1 / If1

  That is, in Equation 1, the constant a is set to a value obtained by dividing the load voltage Vf1 of the LED load 3 at the time of all light by the load current If1. FIG. 3 shows the characteristics of the change in power with respect to the current of the LED power supply device 1, with the constant a being Vf1 / If1 as the constant a1. The power characteristic with respect to the current is a convex quadratic curve (parabola).

  In FIG. 3, it is assumed that the LED load 3 varies in voltage (Vf), and the change in power with respect to the current is in the range of the maximum value and the minimum value as shown in the figure. Here, the power characteristic with respect to the current of the LED power supply device 1 at the constant a1 intersects the power characteristic with respect to the current of the LED load 3 on the apex side of the quadratic curve. Therefore, even if the LED load 3 varies in the range of the Vf maximum value and the Vf minimum value, the power consumption becomes the maximum value 15.4 W and the minimum value 15.1 W, and is almost constant. That is, even if the LED load 3 varies, the variation in power consumption of the LED load 3 is suppressed.

  Further, in the LED power supply device 1 when the constant a is a constant a2 that is 10 times the constant a1, the power characteristic with respect to the current is a substantially straight line having a negative characteristic. The LED power supply device 1 turns on the LED load 3 with power consumption of 17.8 W and 15.0 W with respect to variations in the Vf maximum value and the Vf minimum value of the LED load 3. The variations in power consumption of the LED load 3 are + 15.6% and -2.6%, respectively, with respect to the center value (15.4 W). Even with the constant a2, the variation in the power consumption of the LED load 3 is suppressed within 16% of the center value.

  Further, the LED power supply device 1 when the constant a is a constant a3 that is twice the constant a1 shifts the power characteristic with respect to the current to a lower current side than when the constant a1 and the maximum Vf of the LED load 3 is reached. The LED load 3 is turned on at power consumptions of 16.4 W and 15.2 W with respect to variations in the value and the minimum value of Vf. The variations in power consumption of the LED load 3 are + 6.5% and −1.3%, respectively, with respect to the center value (15.4 W). Even with the constant a3, variation in power consumption of the LED load 3 is suppressed.

  Further, in the LED power supply device 1 when the constant a is a constant a4 which is 0.5 times the constant a1, the power characteristic with respect to the current is a curve with a positive characteristic. The LED power supply device 1 lights the LED load 3 with the power consumption of 15.8 W and 13.2 W with respect to the variation of the Vf maximum value and the Vf minimum value of the LED load 3. The variation in power consumption of the LED load 3 is + 2.6% and −14.3%, respectively, with respect to the center value (15.4 W). Even with the constant a4, the variation in the power consumption of the LED load 3 is suppressed within 15% of the center value.

  In the LED power supply device 1 when the constant a is a constant a5 which is a set value that is as large as possible, the power characteristic with respect to the current becomes a constant current characteristic, and the Vf maximum value and the Vf minimum value of the LED load 3 The LED load 3 is turned on with power consumption of 18.1 W and 14.9 W in response to the variation of. The variations in power consumption of the LED load 3 are + 17.5% and -3.2%, respectively, with respect to the center value (15.4 W). In the LED load 3, the variation in power consumption is suppressed within 18% of the center value.

  Therefore, in this embodiment, the constant a is set to be larger than the value of the constant a4. That is, the constant a is larger than the value (Vf1 / (If1 * 2), that is, Vf1 / If1 * 0.5) obtained by dividing the load voltage Vf1 in the total light of the LED load 3 by twice the load current If1. Is set. Here, the case where the detection voltage value (Vf * R2 / (R1 + R2)) of the load voltage Vf of the LED load 3 is zero is excluded. Thereby, the constant current control with respect to the LED load 3 is removed. Then, the load voltage Vf1 and the load current If1 during all light are determined as shown in FIG. 2 according to the design of the LED load 3.

  The LED load 3 preferably has a power fluctuation range within ± 15%. Therefore, in the present embodiment, the constant a is set in a range of a1 ≦ a <a2 from the viewpoint of controlling the fluctuation range of the power of the LED load 3 within ± 15% and from the viewpoint of control. That is, the constant a is not less than a value (Vf1 / If1) obtained by dividing the load voltage Vf1 at the time of all light by the load current If1, and is set to a value within 10 times the value (Vf1 / If1).

  Next, the operation of the first embodiment will be described.

  When the commercial AC power supply Vs is turned on, a DC voltage is generated across the smoothing capacitor C1 of the AC-DC conversion circuit 6 of the DC output generation circuit 2. The control circuit 12 of the control means 5 controls on / off of the field effect transistor Q1 of the DC-DC conversion circuit 7, adjusts the DC voltage generated between both ends of the smoothing capacitor C1, and thereby adjusts the capacitor of the DC-DC conversion circuit 7. A predetermined DC voltage is generated between both ends of C2. This DC voltage is applied across the LED load 3, and a current flows through the LED load 3. As a result, the LED load 3 is turned on, and visible light is emitted from the LED load 3.

  The control circuit 12 controls on / off of the field effect transistor Q1 so that the current at the intersection of the current-voltage characteristic of the LED power supply device 1 and the current-voltage characteristic of the LED load 3 is supplied to the LED load 3. The field effect transistor Q1 is set so that the total value of the detection voltage value of the load voltage (Vf) and the load current (If) of the LED load 3 becomes the reference value (Vref / k) output from the reference value output circuit 4. ON / OFF control. Thereby, the electric current according to the light control depth k1, k2, ..., k7 of the light control signal output from the external light control apparatus 10 flows into LED load 3. FIG. The LED load 3 lights up at the dimming depths k1, k2,..., K7 of the dimming signal.

  The constant a which is the slope of the control expression 1 controlled by the control circuit 10 is a value (Vf1 / (If1) obtained by dividing the load voltage (Vf1) of the LED load 3 at the time of all light by twice the load current (If1). * 2) Since it is set to a value larger than (2)), the crossing angle at which the current-power characteristic of the LED power supply device 1 and the current-power characteristic of the LED load 3 cross each other becomes large. As a result, as described with reference to FIG. 3, the variation range of the power in the current-power characteristics of the LED power supply device 1 is reduced with respect to the variation in the LED load 3, and the variation in the power consumption of the LED load 3 is suppressed. Is done. In particular, since the range of variation of the LED load 3 during all light is large, variation in power consumption of the LED load 3 during all light is suppressed.

  Then, by setting the constant a of the control expression 1 to a range of a1 ≦ a <a2, the fluctuation range of the power of the LED load 3 is controlled within ± 15% with respect to the variation of the LED load 3. Thereby, the increase in the load current of the LED load 3 can be suppressed, the life of the LED load 3 is ensured, and the variation in light output is also suppressed.

  According to the LED power supply device 1 of the present embodiment, the control means 5 uses the field effect of the DC output generation circuit 2 according to the total value of the detected voltage value of the load voltage Vf of the LED load 3 and the detected current value of the load current If. Since the output of the DC output generation circuit 2 is controlled so as to satisfy the output voltage−a * output current + constant (b) by controlling the on / off of the transistor Q1, the current-power characteristic and the LED load of the LED power supply device 1 are controlled. 3 has an effect that the range of variation in the load power of the LED load 3 can be suppressed with respect to the variation in the LED load 3.

  In addition, the fluctuation range of the load current flowing through the LED load 3 can be suppressed with respect to variations due to individual differences of the LED loads 3 and variations in temperature characteristics during all light and dimming of the LED load 3, It has the effect that the lifetime of the LED load 3 can be secured and the variation in the light output can be suppressed.

  In the present embodiment, a reference value (Vref / Vref /) corresponding to the dimming depths k1, k2,..., K7 of the dimming signal from the reference value output circuit 4 is connected to one input terminal of the comparator 11 of the dimming means 5. However, the present invention is not limited to this, and an LED load 3 that is input to one input terminal of the comparator 11 and is input to the other input terminal of the comparator 11 is not limited thereto. The total value of the detected voltage value of the load voltage (Vf) and the load current (If) may be changed according to the dimming depths k1, k2,..., K7 of the dimming signal.

  Further, the DC-DC conversion circuit 7 of the DC output generation circuit 2 is configured as a step-down chopper circuit having a single field effect transistor Q1. However, the present invention is not limited to this. A step-up / step-down chopper circuit or the like may be used, or an insulating transformer or a flyback circuit may be used.

  In the present embodiment, an example of an analog circuit has been described. However, a control method using a microcomputer or digital processing may be employed.

  Next, a second embodiment of the present invention will be described.

  The illumination device 21 of this embodiment is configured as shown in FIG. In FIG. 4, the same parts as those in FIG.

  The lighting device 21 is a downlight embedded in a ceiling surface or the like, and a circular decorative frame 23 is attached to a lower end side 22a of a substantially cylindrical device body 22 by a rivet 24, and a translucent cover is attached to the decorative frame 23. 25 is arranged. The decorative frame 23 is provided with a reinforcing piece 26 on its outer surface 23a.

  The apparatus main body 22 has a pair of attachment springs 27 and 27 for fixing the apparatus main body 22 to the ceiling surface or the like on both the left and right sides by means of rivets 28. Further, the device main body 22 has four LED loads 3 arranged in a rotationally symmetrical manner inside the lower end side 22a. The LED load 3 is formed on an existing light-emitting body in which a plurality of LED bare chips 9 a are mounted on a substrate 29 and the LED bare chips 9 a are sealed with a translucent resin 30.

  Further, the apparatus main body 22 is provided with the LED power source apparatus 1 shown in FIG. 1 excluding the LED load 3 inside the intermediate side 22b. The LED power supply device 1 supplies power to the LED bare chip 9 a of each LED load 3. A terminal block 31 for connecting a power line (not shown) from the AC power supply is disposed on the upper surface side 22c of the apparatus main body 22.

  Since the illumination device 21 of the present embodiment includes the LED power supply device 1 shown in FIG. 1, it is possible to suppress variations in power consumption of the LED loads 3 and to stabilize illumination light in which variations in light output are suppressed. And has an effect that the light can be emitted.

  The lighting device 21 is formed as an embedded downlight. However, the lighting device 21 is not limited thereto, and is a long embedded type, a direct mounting type or a hanging type LED device including the LED power supply device 1 or an LED. It may be formed in a lamp device such as a light bulb.

DESCRIPTION OF SYMBOLS 1 ... LED power supply device, 2 ... DC output production | generation circuit, 3 ... LED load, 4 ... Reference value output circuit, 5 ... Control means, 21 ... Illumination device, 22 ... Apparatus main body, Q1 ... Field effect transistor as a switching element

Claims (3)

A DC output generation circuit including a switching element and outputting a DC voltage corresponding to an on / off operation of the switching element;
An LED load connected between the outputs of the DC output generation circuit;
By controlling on / off of the switching element according to the total value of the detected voltage value of the load voltage applied to the LED load and the detected current value of the load current flowing through the LED load, the output of the DC output generation circuit is as follows: Control means for controlling to satisfy Equation 1;
An LED power supply device comprising:
Equation 1; output voltage = −a * output current + constant (b)
However, except when the detection voltage value of the load voltage is zero, a> a1 * 0.5, where a1 is obtained by dividing the load voltage applied to the LED load at the time of all light by the load current. Value.   2. The LED power supply device according to claim 1, wherein a is in a range of a1 ≦ a <a2. Here, a2 is a1 * 10. An LED power supply device according to claim 1 or 2;
A device body in which the LED power supply device is disposed;
An illumination device comprising:

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