JP6760102B2 - Lighting device and lighting equipment - Google Patents

Description

The present invention relates to a lighting device and a luminaire.

Patent Document 1 discloses a lighting device including a back converter circuit. In the back converter circuit, the input voltage is time-divided by a switching element and smoothed by an inductor and a capacitor. As a result, the input voltage is converted to the target voltage.

Japanese Unexamined Patent Publication No. 2011-155747

However, when the lighting device is stored in a predetermined space such as a lighting fixture, it may be necessary to reduce the size of the lighting device. In general, passive components such as coils and capacitors occupy a large area in a lighting device. Therefore, it may be necessary to reduce the size of the passive component. As a method of realizing miniaturization of passive components, it is conceivable to increase the switching frequency of the back converter circuit. However, the performance of the switching element may not catch up with the increase in the switching frequency.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a lighting device and a lighting fixture capable of miniaturizing a passive component.

The lighting device according to the present invention is a back converter circuit including a plurality of switching elements connected in parallel, an inductor connected in series with the plurality of switching elements, and a capacitor connected in parallel to the output terminal. A control device for controlling the lighting of the light source by sequentially turning on and off the plurality of switching elements, the secondary winding of the inductor is connected to the control device, and the control device is used for the plurality of switching. after turning off the one of the elements, the output voltage of the secondary winding turns from decrease to increase, Ru oz next switching element.

In the lighting device according to the present invention, a plurality of switching elements are turned on and off in order. Therefore, the operating frequency of the back converter circuit can be increased while maintaining the operating frequency of each switching element low. Therefore, the passive component can be miniaturized.

It is a circuit block diagram of the lighting fixture which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the lighting device which concerns on Embodiment 1. FIG. It is a figure explaining resonance. It is a figure explaining the frequency dependence of a coil current. It is a figure explaining a switching loss.

The lighting device and the luminaire according to the embodiment of the present invention will be described with reference to the drawings. The same or corresponding components may be designated by the same reference numerals and the description may be omitted.

Embodiment 1.
FIG. 1 is a circuit block diagram of the lighting fixture 100 according to the first embodiment. The lighting fixture 100 according to the present embodiment includes an LED module 11. The LED module 11 includes a plurality of LEDs 11a. The LED 11a is a light source. A plurality of LEDs 11a are connected in series. The number of LEDs 11a included in the LED module 11 may be plural.

The luminaire 100 includes a lighting device 12. The LED module 11 is connected to the output end of the lighting device 12. The lighting device 12 lights the LED 11a. The lighting device 12 includes a DC power supply 2. The DC power supply 2 is connected to the AC power supply 7 via a wall switch. The AC power source 7 is an external power source. The rectifier circuit 8 included in the DC power supply 2 is connected to the AC power supply 7. A capacitor 9 is connected in parallel to the output terminal of the rectifier circuit 8. The capacitor 9 is a smoothing capacitor.

A first voltage divider circuit is connected in parallel to the capacitor 9. The first voltage divider circuit is composed of a resistor 31 and a resistor 32 connected in series. The voltage applied to both ends of the capacitor 9 is divided by the resistors 31 and 32 and input to the control device 40. The resistors 31 and 32 divide the voltage rectified by the rectifier circuit 8. The resistors 31 and 32 output the voltage waveform of the divided voltage to the control device 40. The control device 40 traces the voltage waveform input from the first voltage dividing circuit. The voltage waveform traced by the control device 40 is referred to as control information when controlling the on / off of the first switching element Q1.

One end of the inductor 10 is connected to the high potential side of the rectifier circuit 8. The other end of the inductor 10 is connected to the first terminal of the first switching element Q1 and the anode of the diode 14. The first switching element Q1 is a MOSFET (Metal-Oxide-Semiconductor Field-Effective Transistor). Further, the first terminal of the first switching element Q1 is a drain.

The second terminal of the first switching element Q1 is connected to the low potential side of the rectifier circuit 8. The second terminal of the first switching element Q1 is a source. Further, the control terminal of the first switching element Q1 is connected to the control device 40. The control terminal is a terminal for switching between the first terminal and the second terminal. The control terminal is a gate. The positive electrode of the capacitor 17 is connected to the cathode of the diode 14. The capacitor 17 is an electrolytic capacitor. The negative electrode of the capacitor 17 is connected to the low potential side of the rectifier circuit 8.

The inductor 10, the first switching element Q1, the diode 14 and the capacitor 17 form a step-up chopper circuit. A second voltage divider circuit is connected in parallel to the capacitor 17. The second voltage divider circuit is composed of a resistor 15 and a resistor 16 connected in series. The voltage applied to both ends of the capacitor 17 is divided by the resistors 15 and 16 and input to the control device 40.

The resistors 15 and 16 are provided at the output end of the DC power supply 2. The resistors 15 and 16 detect the output voltage of the DC power supply 2. The detection voltage applied to the resistor 16 is input to the control device 40. Based on this detected voltage, the control device 40 turns on / off the first switching element Q1 so that the output voltage of the DC power supply 2 becomes constant. From the above, the DC power supply 2 is configured.

The lighting device 12 includes a back converter circuit 3. The back converter circuit 3 is connected to the output of the DC power supply 2. The positive electrode of the capacitor 17 is connected to the first terminal of the second switching element Q2. The second switching element Q2 is a MOSFET. The first terminal of the second switching element Q2 is a drain. The cathode of the diode 21 is connected to the second terminal of the second switching element Q2. The second terminal of the second switching element Q2 is a source. The control terminal of the second switching element Q2 is connected to the control device 40. The control terminal is a gate.

The anode of the diode 21 is connected to the negative electrode of the capacitor 17. That is, a series circuit including the second switching element Q2 and the diode 21 is connected in parallel with the capacitor 17.

The lighting device 12 includes a third switching element Q3. The third switching element Q3 is the same MOSFET as the second switching element Q2. The first terminal of the third switching element Q3 is connected to the first terminal of the second switching element Q2. The second terminal of the third switching element Q3 is connected to the second terminal of the second switching element Q2. The third switching element Q3 is connected in parallel with the second switching element Q2. The control terminal of the third switching element Q3 is connected to the control device 40. Similar to the second switching element Q2, in the third switching element Q3, the first terminal is a drain, the second terminal is a source, and the control terminal is a gate.

The inductor 22, the capacitor 23, and the detection resistor 24 are connected in this order to form a series circuit. This series circuit is connected in parallel to the diode 21. The inductor 22 is connected in series with the second switching element Q2 and the third switching element Q3. The inductor 22 has a secondary winding 26. One end of the secondary winding 26 of the inductor 22 is connected to the control device 40. The other end of the secondary winding 26 of the inductor 22 is connected between the anode of the diode 21 and the detection resistor 24. The inductor 22 is used as a choke coil.

The capacitor 23 is connected in parallel to the output end of the back converter circuit 3. A third voltage divider circuit is connected in parallel to the capacitor 23. The third voltage divider circuit is composed of a resistor 51 and a resistor 52 connected in series. The voltage applied to both ends of the capacitor 23 is divided by the resistors 51 and 52 and input to the control device 40.

The detection resistor 24 is used to detect the LED current flowing through the LED 11a. A detection voltage corresponding to the LED current is applied to the detection resistor 24. The detection voltage is input to the control device 40. Further, the bottom voltage detected by the secondary winding 26 is input to the control device 40. The control device 40 turns on / off the second switching element Q2 and the third switching element Q3 so that the LED current becomes constant based on the bottom voltage and the detection voltage detected by the detection resistor 24.

The third voltage dividing circuit is provided at the output end of the lighting device 12. The third voltage divider circuit is used to detect the voltage applied to the LED module 11. The detection voltage applied to the resistor 52 is input to the control device 40. Based on this detected voltage, the control device 40 detects whether or not the LED module 11 is connected and a voltage abnormality. From the above, the back converter circuit 3 is configured.

The control device 40 controls the lighting of the LED 11a. As the control device 40, a microcomputer, which is a control device for a digital power supply, is used. Further, an arithmetic unit such as a DSP (Digital Signal Processor) may be used. Further, the lighting device 12 includes a control power supply generation circuit 110. The control power generation circuit 110 is connected to the positive electrode of the capacitor 17. The control power supply generation circuit 110 generates and outputs a power supply for the control device 40 based on the output voltage rectified and boosted by the DC power supply 2. The power supply of the control device 40 is supplied from the control power supply generation circuit 110.

The control device 40 includes two control circuits 41 and 42, a storage unit 43, an A / D conversion circuit 44, and a processing device 45. The two control circuits 41 and 42, the storage unit 43, the A / D conversion circuit 44, and the processing device 45 are connected to each other via an internal bus. The control circuit 41 outputs a PWM (Pulse Width Modulation) signal to the first switching element Q1. The control circuit 42 outputs a PWM signal to the second switching element Q2 and the third switching element Q3. The PWM signal switches the first switching element Q1, the second switching element Q2, and the third switching element Q3.

The storage unit 43 includes, for example, a non-volatile memory. The storage unit 43 stores an arithmetic program executed by the processing device 45 and various data used for the arithmetic. The storage unit 43 is provided so that data can be written and read from the outside. The processing device 45 calculates the on-time in the switching control of the first switching element Q1, the second switching element Q2, and the third switching element Q3.

The detection voltage from the first voltage dividing circuit, the second voltage dividing circuit, the third voltage dividing circuit, the secondary winding 26 and the detection resistor 24 is input to the control device 40. The A / D conversion circuit 44 converts these detected voltages into digital values. The processing device 45 executes arithmetic processing using this digital value. A preset target voltage is stored in the storage unit 43. The control device 40 performs constant voltage control by adjusting the on-time of the first switching element Q1 so that the output voltage of the DC power supply 2 matches the target voltage.

The luminaire 100 includes a dimmer 28 and a dimming signal interface (I / F) circuit 4. A dimming command value from the dimmer 28 is input to the control device 40 via the dimming signal I / F circuit 4. The control device 40 has the second switching element Q2 and the third switching element Q3 based on the LED current detected by the detection resistor 24 so that the LED current and the target current determined based on the dimming command value match. Adjust the on-time of.

The lighting device 12 includes a receiving unit 101. The receiving unit 101 receives the wireless signal from the remote controller 20. The receiving unit 101 is connected to the control device 40. The radio signal is input to the control device 40 via the receiving unit 101. The radio signal includes information such as a dimming command value. Further, the control device 40 transmits a wireless signal to the remote controller 20 via the receiving unit 101.

FIG. 2 is a diagram illustrating the operation of the lighting device 12 according to the first embodiment. Next, the switching timing of the second switching element Q2 and the third switching element Q3 will be described. In FIG. 2, I22 shows the coil current flowing through the inductor 22. Q2Id indicates the current flowing through the first terminal of the second switching element Q2. Q3Id indicates the current flowing through the first terminal of the third switching element Q3.

Further, Vds indicates a voltage applied between the first terminal and the second terminal of the second switching element Q2 and the third switching element Q3. Q2Vgs indicates the voltage applied between the control terminal and the second terminal of the second switching element Q2. Q3Vgs indicates the voltage applied between the control terminal and the second terminal of the third switching element Q3.

First, the voltage Q2Vgs is turned on. As a result, the second switching element Q2 is turned on. As a result, the voltage Vds drops, and the coil current I22 flows through the inductor 22. The state in which the second switching element Q2 is turned on is maintained for the on time determined by the control device 40. When the on time elapses, the voltage Q2Vgs is turned off. As a result, the second switching element Q2 is turned off. As a result, the voltage Vds increases and the coil current I22 decreases.

The coil current I22 decreases with the passage of time. When the coil current I22 reaches zero, the voltage Vds begins to resonate. When the control device 40 detects the bottom of the resonance of the voltage Vds, it turns on the voltage Q3Vgs. The bottom of resonance is a state in which the voltage Vds is the minimum in the resonance state. As a result, the third switching element Q3 is turned on.

As a result, the voltage Vds drops and the coil current I22 flows. The state in which the third switching element Q3 is turned on is maintained for the on time determined by the control device 40. When the on time elapses, the voltage Q3Vgs is turned off. As a result, the third switching element Q3 is turned off. As a result, the voltage Vds increases and the coil current I22 decreases. When the coil current I22 reaches zero, the voltage Vds begins to resonate. When the control device 40 detects the bottom of the resonance of the voltage Vds, it turns on the voltage Q2Vgs. As a result, the second switching element Q2 is turned on.

FIG. 3 is a diagram illustrating resonance. When the coil current I22 is zero, the voltage Vds resonates. The dotted line 62 shows the resonance waveform of the voltage Vds. The control device 40 monitors a change in the output voltage or output current of the secondary winding 26 of the inductor 22. When the output voltage of the secondary winding 26 becomes the minimum in the resonance state, the control device 40 determines that it is the bottom 61 of the resonance. That is, when the output voltage of the secondary winding 26 changes from decreasing to increasing in the resonance state, the control device 40 determines that it is the bottom 61 of the resonance. As a result, the bottom 61 of resonance, which is the minimum value of the voltage Vds in the resonance state, is detected.

By repeating the above operation, the second switching element Q2 and the third switching element Q3 are turned on alternately. Therefore, the second switching element Q2 and the third switching element Q3 operate at half the operating frequency of the inductor 22 and the capacitor 23. Therefore, the operating frequencies of the inductor 22 and the capacitor 23 can be set higher than the switching frequencies of the second switching element Q2 and the third switching element Q3, respectively. Here, the operating frequencies of the inductor 22 and the capacitor 23 indicate the frequencies of the currents flowing through the inductor 22 and the capacitor 23.

FIG. 4 is a diagram illustrating the frequency dependence of the coil current I22. In FIG. 4, I0 and QId show the current waveforms of the back converter circuit according to the comparative example. The back converter circuit according to the comparative example includes only one switching element Q. I0 indicates the coil current flowing through the inductor 22 in the back converter circuit according to the comparative example. Further, QId indicates the current flowing through the first terminal of the switching element Q in the back converter circuit according to the comparative example. In FIG. 4, I22, Q2Id and Q3Id are current waveforms of the back converter circuit 3 according to the present embodiment.

It is assumed that the operating frequency of the back converter circuit according to the comparative example is half the operating frequency of the back converter circuit 3 according to the present embodiment. That is, it is assumed that the operating frequency of the inductor 22 according to the comparative example is half the operating frequency of the inductor 22 according to the present embodiment. Further, it is assumed that the back converter circuit according to the comparative example and the back converter circuit 3 according to the present embodiment have the same amount of current flowing through the LED module 11 in a unit time.

The back converter circuit according to the comparative example and the back converter circuit 3 according to the present embodiment have the same amount of current flowing through the inductor 22 per unit time. Therefore, when the area per cycle of the coil current I0 is S0 and the area of the coil current I22 per cycle is S1 or S2, S0 = S1 + S2. Further, the peak currents of the coil current I0 and the coil current I22 are equal. At this time, as shown in FIG. 4, the inclination of the coil current I22 is larger than that of the coil current I0. That is, the amount of change per unit time of the coil current I22 is larger than that of the coil current I0.

From the above, when the amount of current flowing through the LED module 11 in a unit time is the same, the amount of change in the coil current I22 per unit time increases as the inductor 22 operates at a higher speed. In general, the larger the amount of change in the current flowing through the inductor 22 per unit time, the smaller the inductance value L of the inductor 22 can be. Therefore, the core and winding specifications of the inductor 22 can be reduced, and the inductor 22 can be miniaturized. Here, the winding specification is, for example, the thickness or the number of windings of the winding. From the above, the inductor 22 can be miniaturized by operating the inductor 22 at high speed.

Further, in general, the ripple component can be suppressed by increasing the operating frequency. Therefore, if the operating frequency is increased, a low-capacity capacitor can be used as the capacitor 23. Therefore, the capacitor 23 can be miniaturized by increasing the operating frequency.

From the above, the larger the operating frequency, the smaller the passive component can be. In the present embodiment, the operating frequencies of the inductor 22 and the capacitor 23 can be increased while the switching frequencies of the second switching element Q2 and the third switching element Q3 are maintained low. That is, the passive component can be miniaturized while satisfying the rating of the switching performance of the second switching element Q2 and the third switching element Q3. Therefore, the lighting device 12 can be miniaturized.

Further, according to the present embodiment, the burden on the second switching element Q2 and the third switching element Q3 can be reduced. The burden borne by the second switching element Q2 and the third switching element Q3 is, for example, an internal power loss that occurs when the second switching element Q2 and the third switching element Q3 switch at high speed. Internal power loss is also called switching loss.

FIG. 5 is a diagram for explaining the switching loss. In FIG. 5, the current flowing through the first terminal of the switching element is defined as Id. Further, the voltage applied between the first terminal and the second terminal of the switching element is defined as Vds. When the switching element is turned off, the current Id decreases while the voltage Vds increases. The area of the portion 63 where the current Id and the voltage Vds overlap corresponds to the switching loss.

Although there are individual differences depending on the switching element, in general, the faster the switching element is switched, the larger the area of the portion 63 where the current Id and the voltage Vds overlap. In particular, in the vicinity of the limit value of the response speed of the switching element, the area of the portion 63 where the current Id and the voltage Vds overlap is often large.

On the other hand, in the present embodiment, the switching frequency of each of the second switching element Q2 and the third switching element Q3 can be set to half the operating frequency of the back converter circuit 3. Therefore, in the back converter circuit 3 according to the present embodiment, the area of the portion 63 where the current Id and the voltage Vds overlap can be reduced as compared with the back converter circuit having the same operating frequency and having only one switching element. Therefore, switching loss can be suppressed while setting the operating frequency of the back converter circuit 3 high. Here, the operating frequency of the back converter circuit 3 indicates the frequency of the current flowing through the inductor 22.

Further, in the present embodiment, the second switching element Q2 and the third switching element Q3 are alternately turned on and off. Therefore, the ratio of the off time to the on time can be increased in each of the second switching element Q2 and the third switching element Q3 as compared with the case where only one switching element is provided. That is, the period in which the current Id flows can be shortened in each of the second switching element Q2 and the third switching element Q3. Therefore, it is possible to suppress the internal heat generation caused by the flow of the current Id.

The lighting device 12 according to the present embodiment is a two-converter system including a DC power supply 2 and a back converter circuit 3. As a modification of this, the lighting device 12 does not have to include the DC power supply 2. The lighting device 12 may be a one-converter system including only the back converter circuit 3.

Further, in the present embodiment, the back converter circuit 3 includes two switching elements Q2 and Q3. The number of switching elements included in the back converter circuit 3 is not limited to two, and may be a plurality. In this case, the back converter circuit 3 includes a plurality of switching elements connected in parallel. Further, the control device 40 sequentially turns on and off a plurality of switching elements. When the control device 40 turns on and off three or more switching elements connected in parallel in order, the burden on each switching element can be further reduced.

The technical features described in each embodiment may be used in combination as appropriate.

100 lighting equipment, 12 lighting device, Q2 2nd switching element, Q3 3rd switching element, 3 back converter circuit, 40 controller, 22 inductor, 23 capacitor, 26 secondary winding, 11a LED

Claims (3)

A back converter circuit including a plurality of switching elements connected in parallel, an inductor connected in series with the plurality of switching elements, and a capacitor connected in parallel at the output end .
A control device that controls the lighting of the light source by sequentially turning on and off the plurality of switching elements.
Equipped with a,
The secondary winding of the inductor is connected to the control device and
Wherein the control device, after turning off the one of the plurality of switching elements, the output voltage of the secondary winding turns from decrease to increase, the lighting device according to claim ounces Rukoto the next switching element. The lighting device according to claim 1, wherein the control device turns on and off the plurality of switching elements so that the current flowing through the light source becomes constant. The lighting device according to claim 1 or 2 ,
With the light source
Lighting equipment characterized by being equipped with.

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