JP6756200B2 - LED lighting circuit and LED lighting device - Google Patents

Description

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

The power supply device of Patent Document 1 includes two power supply circuits for lighting two LEDs and two control circuits for controlling the outputs of the two power supply circuits. Each power supply circuit includes a power factor improving circuit and a DC / DC converter, and each control circuit controls each power factor improving circuit and the output of each DC / DC converter according to the dimming rate.

Japanese Unexamined Patent Publication No. 2012-22880

Generally, the power factor improving circuit is designed based on the maximum required power. Therefore, in a light load such as low dimming, the power factor or efficiency in the power factor improving circuit may decrease as the output power deviates from the optimum design point. In particular, when each system is independently controlled in a two-system output LED lighting circuit including two sets of power factor improvement circuits and a DC / DC converter, the power factor and efficiency are reduced due to the light load of each system. Then, the power factor and efficiency of both systems as a whole will decrease.

Therefore, an object of the present invention is to provide a two-system output LED lighting circuit capable of maintaining a high power factor and efficiency even at a light load such as low dimming, and an LED lighting device using the same. ..

The LED lighting circuit of the present disclosure includes a first power factor improving circuit to which the rectified output of the AC power supply is input, a second power factor improving circuit to which the rectified output of the AC power supply is input, and a first or second power factor improving circuit. A first DC / DC converter that supplies a DC current corresponding to the first dimming signal to the first LED array using the output voltage of the power factor improving circuit as a voltage source, and a first or second power factor improving circuit. A second DC / DC converter that supplies a DC current corresponding to the second dimming signal to the second LED array using the output voltage of the above as a voltage source, and a first DC / DC converter for the first and second DC / DC converters, respectively. And the dimming command unit that outputs the second dimming signal, the ratio of the total dimming output power to the total maximum output power of the first and second DC / DC converters based on the first and second dimming signals. It includes a load factor calculation unit that calculates the load factor, and a central control unit that includes an operation command unit that stops one of the first and second force factor improvement circuits when the load factor is equal to or less than a threshold value.

According to the LED lighting circuit of the present disclosure, one of the first and second power factor improving circuits is stopped and independent operation is applied at the time of low dimming, so that the operating side power factor improving circuit has a load factor of the load factor. The increase allows the operation to approach the optimum design point. Therefore, it is possible to maintain a high power factor and efficiency even in a light load such as low dimming in a two-system output LED lighting circuit.

In the LED lighting circuit of the first embodiment, the central control unit acquires a difference value obtained by subtracting the cumulative value of the stop time of the second power factor improvement circuit from the cumulative value of the stop time of the first power factor improvement circuit. When the cumulative difference acquisition unit and the difference value exceed a predetermined time in the positive direction, the operation command unit operates the first power factor improvement circuit and stops the second power factor improvement circuit, and the difference value is in the negative direction. When the time exceeds a predetermined time, the operation command unit further includes a switching unit for stopping the first power factor improving circuit and operating the second power factor improving circuit. As a result, the stop times of the first and second power factor improving circuits are equalized, that is, the operating times are equalized, and the lifespan of both are averaged. Therefore, the situation where one of the first and second power factor improving circuits reaches the end of their life earlier than the other is prevented, and the life of the LED lighting circuit as a whole is extended.

In the LED lighting circuit of the second form, the maximum output power of the first power factor improving circuit corresponds to the first maximum output power of the first DC / DC converter, and the maximum output of the second power factor improving circuit. When the power corresponds to the second maximum output power of the second DC / DC converter and the first maximum output power is higher than the second maximum output power, the central control unit determines the second maximum output power. When the individual load factor, which is the ratio of the total dimming output power to, is less than or equal to a predetermined value, the operation command unit stops the first power factor improvement circuit and operates the second power factor improvement circuit to operate the individual load factor. When the rate exceeds a predetermined value, the operation command unit further includes a selection unit for stopping the second power factor improving circuit and operating the first power factor improving circuit. As a result, the individual load factor of each of the first and second power factor improving circuits is maximized within the range of the maximum output power or less, and high power factor and efficiency can be obtained for the LED lighting circuit as a whole.

In the LED lighting circuit of the third embodiment, the central control unit further includes a voltage detection unit that detects the power supply voltage of the AC power supply, and the operation command unit is configured to raise the threshold value with respect to the increase in the power supply voltage. .. Alternatively, the load factor calculation unit performs the calculation so that the load factor is relatively low when the power supply voltage is relatively high as compared with the case where the power supply voltage is relatively low. As a result, in the central control unit, the light load state is overestimated with respect to the increase in the power supply voltage due to the difference or fluctuation of the AC power supply, and the first and second power factor improving circuits operate independently. Migration conditions are optimized.

As one circuit configuration, the low potential output end of the first power factor improvement circuit and the low potential output end of the second power factor improvement circuit are connected, and the high potential output end of the first power factor improvement circuit and the second It is connected to the high potential output end of the power factor improvement circuit. As a result, continuous switching between the parallel operation and the independent operation of the power factor improving circuit in the two-system output is realized with a simple configuration.

In the LED lighting circuit of the fourth form, the output voltage during operation of the first power factor improvement circuit and the output voltage during operation of the second power factor improvement circuit are substantially equal, and the first power factor improvement The low potential output end of the circuit and the low potential output end of the second power factor improvement circuit are connected, and the high potential output end of the first power factor improvement circuit and the high potential output end of the second power factor improvement circuit A pair of antiparallel diodes connected between the two are provided. As a result, during the parallel operation of the first and second power factor improving circuits, both the antiparallel diodes are turned off, and the system including the first power factor improving circuit and the first DC / DC converter and the first Independence from the system including the power factor improving circuit of 2 and the second DC / DC converter can be obtained. Therefore, for example, when the maximum output powers of both systems are different from each other, the design consistency in parallel operation is maintained.

In the LED lighting circuit of the fifth embodiment, the first power factor improving circuit has a first switching unit that switches the input voltage, a first diode that rectifies the switching output of the first switching unit, and a first. A second smoothing capacitor in which the rectified output of the diode is charged, and a second power factor improving circuit rectifies the switching output of the second switching unit that switches the input voltage and the second switching unit. It has a diode and a second smoothing capacitor in which the rectified output of the second diode is charged, and the low potential side node of the first smoothing diode and the low potential side node of the second smoothing capacitor are connected to each other. A third diode connected with this direction as the rectifying direction between the anode of the first diode and the cathode of the second diode, and this direction between the anode of the second diode and the cathode of the first diode. A fourth diode connected to the diode is provided. As a result, the first smoothing capacitor is not connected to the second DC / DC converter, and the second smoothing capacitor is not connected to the first DC / DC converter. Therefore, the independence of the first smoothing capacitor and the first DC / DC converter and the second smoothing capacitor and the second DC / DC converter can be obtained. Therefore, for example, in the first and second DC / DC converters having different maximum output powers, in a configuration in which the first and second smoothing capacitors having different capacities are adopted, even when the power factor improving circuit is operated independently. The design consistency of the first and second smoothing capacitors and the first and second DC / DC converters is maintained. Further, when viewed from the first or second power factor improving circuit, the state in which the first and second smoothing capacitors are connected in parallel is maintained regardless of the operation or stop, so that the power factor improving circuit operates independently. Even at times, an increase in output ripple is avoided.

In the LED lighting circuit of the sixth embodiment, the first power factor improving circuit includes a first smoothing capacitor between the output ends, and the second power factor improving circuit includes a second smoothing capacitor between the output ends. The low potential side node of the first smoothing capacitor and the low potential side node of the second smoothing capacitor are connected, and the high potential side node of the first smoothing capacitor and the high potential side input end of the first DC / DC converter are connected. This is used for the wiring between the third diode, which is inserted and connected with this direction as the rectifying direction, and the high potential side node of the second smoothing capacitor and the high potential side input end of the second DC / DC converter. This direction is connected as the rectification direction between the fourth diode inserted and connected with the direction as the rectification direction, the high potential side node of the first smoothing capacitor, and the high potential side input end of the first DC / DC converter. A fifth diode and a sixth diode connected between the high potential side node of the second smoothing capacitor and the high potential side input end of the first DC / DC converter with this direction as the rectifying direction are provided. Be done. As a result, the first smoothing capacitor is not connected to the second power factor improving circuit, and the second smoothing capacitor is not connected to the first power factor improving circuit. Therefore, during the independent operation of the power factor improving circuit, the smoothing capacitor included in the stopped power factor improving circuit is completely de-energized, so that the life of each smoothing capacitor is expected to be extended. Moreover, since the life of the power factor improving circuit tends to depend on the life of the smoothing capacitor (electrolytic capacitor), the cumulative value of the stop time of the power factor improving circuit and the cumulative value of the non-energized time of the smoothing capacitor match. When this configuration is applied to the first embodiment, the accuracy of life averaging is improved.

The LED lighting device of the present disclosure includes any of the above LED lighting circuits and first and second LED arrays. As a result, an LED lighting device capable of maintaining a high power factor and efficiency even at a light load such as low dimming is realized.

It is a block diagram which shows the LED lighting circuit and LED lighting apparatus of 1st Embodiment. It is a block diagram which shows the LED lighting circuit and LED lighting apparatus of the 2nd Embodiment. It is a block diagram which shows the LED lighting circuit and LED lighting apparatus of the 3rd Embodiment. It is a block diagram which shows the LED lighting circuit and LED lighting apparatus of 4th Embodiment. It is a block diagram which shows the LED lighting circuit and LED lighting apparatus of 5th Embodiment. It is a block diagram which shows the LED lighting circuit and LED lighting apparatus of 6th Embodiment. It is a block diagram which shows the modification of 5th and 6th Embodiment.

<First Embodiment>
FIG. 1 shows a block diagram of an LED lighting circuit 1 according to the first embodiment of the present invention and an LED lighting device 3 including the LED lighting circuit 1. The LED lighting device 3 includes an LED lighting circuit 1 and LED arrays 2A and 2B, and the LED lighting circuit 1 includes converter circuits 5A and 5B and a central control unit 40. The converter circuits 5A and 5B are supplied with an AC power supply AC such as a commercial power supply to supply a variable DC current to the LED arrays 2A and 2B, respectively. As described above, the LED lighting device 3 has a system A including a dimmable converter circuit 5A and an LED array 2A, and a system B including a dimmable converter circuit 5B and an LED array 2B. The LED lighting circuit 1 and the LED lighting device 3 having such a multi-system output configuration and dimmable can be applied to, for example, road lights, tunnel lights, and the like.

The converter circuit 5A includes a rectifier circuit 10A, a power factor improvement circuit (PFC) 20A and a DC / DC converter 30A, and the converter circuit 5B includes a rectifier circuit 10B, a power factor improvement circuit (PFC) 20B and a DC / DC converter 30B. The output states of the converter circuits 5A and 5B are controlled by the central control unit 40. Further, since the system A and the system B have the same configuration, only the system A will be described below. Then, if the end of the code of each element of the system A is replaced with B or b from A or a, the description of the system B is established.

The rectifier circuit 10A includes a diode bridge (not shown) and an input capacitor connected between the output ends of the diode bridge. The AC input voltage is full-wave rectified by the diode bridge, a pulsating voltage appears in the input capacitor, and this pulsating voltage becomes the input voltage of the PFC 20A. A single rectifier circuit may be shared by the systems A and B, and the rectifier output of the rectifier circuit may be branched into PFC 20A and 20B.

The PFC 20A includes a switching element 21A, an inductor 22A, a diode 23A, a smoothing capacitor 24A, and a PWM control circuit 25A, and constitutes a boost chopper circuit. The energy stored in the inductor 22A when the switching element 21A is turned on is charged to the smoothing capacitor 24A via the diode 23A when the switching element 21A is turned off. The switching element 21A is PWM controlled by the PWM control circuit 25A. The switching element 21A and the inductor 22A are also collectively referred to as a switching unit. By properly designing and controlling the switching unit, the input current from the AC power supply AC becomes close to a sine wave, and the input power factor is improved.

The DC / DC converter 30A may be any form of DC / DC converter such as a step-down chopper circuit (that is, a back converter), a flyback converter, and a backboost converter. The DC / DC converter 30A converts the voltage of the smoothing capacitor 24A into a direct current corresponding to the dimming rate Da indicated by the dimming signal SDa from the central control unit 40, and supplies this direct current to the LED 2A. That is, the DC / DC converter 30A dimmes and lights the LED array 2A. In the present disclosure, "dimming" may include not only dimming lighting with a dimming rate of less than 100% but also all-light lighting with a dimming rate of 100%.

In the present embodiment, the wiring Ha between the high potential side output end of the PFC 20A and the high potential side input end of the DC / DC converter 30A is the high potential side input of the PFC 20B and the DC / DC converter 30B. It is connected to the wiring Hb between the ends via the wiring Lh. Further, the wiring Ga between the low potential side output end of the PFC 20A and the low potential side input end of the DC / DC converter 30A is the connection between the low potential side output end of the PFC 20B and the low potential side input end of the DC / DC converter 30B. It is connected to the wiring Gb between them via the wiring Lg. Therefore, the PFC 20A can supply power to the DC / DC converters 30A and 30B, and the PFC 20B can supply power to the DC / DC converters 30A and 30B. In this way, the high potential output end of the PFC 20A and the high potential output end of the PFC 20B are connected, and the low potential output end of the PFC 20A and the low potential output end of the PFC 20B are connected, so that the PFC 20A and 20B in the two system outputs are connected. Continuous switching between parallel operation and independent operation is realized with a simple configuration.

The central control unit 40 includes a dimming input unit 41, a dimming command unit 42, a load factor calculation unit 43, an operation command unit 44, a cumulative difference acquisition unit 45, and a switching unit 46. The central control unit 40 is composed of, for example, a microcomputer, and includes a CPU and a memory (not shown). The dimming command unit 42, the load factor calculation unit 43, the operation command unit 44, the cumulative difference acquisition unit 45, and the switching unit 46 form a part of the CPU and can transfer data between each other and with the memory. Be connected.

The dimming input unit 41 is an input interface that receives a dimming instruction from the outside of the LED lighting device 3. This dimming instruction may individually indicate the dimming rate of the LED arrays 2A and 2B, or simultaneously instruct both dimming rates (the same dimming rate or a combination of different dimming rates). It may be something to do.

The dimming command unit 42 outputs dimming signals SDa and SDb indicating the dimming rate to the DC / DC converters 20A and 20B, respectively, based on the input dimming instruction. As a result, the DC / DC converters 20A and 20B control the output current based on the dimming rates Da and Db shown in the dimming signals SDa and SDb, respectively, to dimm the LED arrays 2A and 2B.

The load factor calculation unit 43 calculates the load factor R, which is the ratio of the total dimming output power to the total maximum output power of the DC / DC converters 30A and 30B, based on the dimming rates Da and Db. Assuming that the maximum output powers of the DC / DC converters 30A and 30B are Pa and Pb, the total maximum output power Pmax = Pa + Pb, the total dimming output power Pdim = Pa × Da + Pb × Db, and the load factor R is It is calculated as R = Pdim / Pmax = (Pa × Da + Pb × Db) / (Pa + Pb). However, in this embodiment, it is assumed that Pa = Pb, and the load factor R is R = (Da + Db) / 2.

The operation command unit 44 performs a parallel operation of operating both the PFC 20A and 20B based on the load factor R calculated by the load factor calculation unit 43, or performs a single operation of stopping one of the PFC 20A and 20B. Decide if you want to do it. Specifically, when the load factor R exceeds the threshold value α (for example, 50%), the operation command unit 44 operates both the PFC 20A and 20B to apply the parallel operation. On the other hand, when the load factor R is equal to or less than the threshold value α, one of the PFC 20A and 20B is stopped and the independent operation is applied. Which of PFC20A and 20B is to be operated / stopped will be described later. Based on the above determination, the operation command unit 44 outputs ON / OFF signals SPA and SPb to the PWM control circuits 25A and 25B, respectively, to control the operation / stop of the PFC 20A and 20B. The transition between the parallel operation and the independent operation in the PFC 20A and 20B can be applied in both directions in response to the dimming instruction.

For example, when α = 50%, Pa = Pb, and Da = Db = 50%, if both PFC 20A and 20B operate, the load factor R becomes 50%. Here, since the load factor R is equal to or less than the threshold value α, one of the PFCs 20A and 20B is stopped by the operation command unit 44, whereby the other can operate at the load factor of 100%.
Further, as another example, when α = 50%, Pa = Pb, Da = 50%, and Db = 25%, the load factor R is 37.5%. Here, since the load factor R is equal to or less than the threshold value α, one of the PFCs 20A and 20B is stopped by the operation command unit 44, whereby the other can operate at the load factor of 75%.

Generally, since the PFC is designed for its maximum output power, it is desirable from the viewpoint of optimum operation that each load factor is operated in a state close to 100%. On the contrary, if each load factor exceeds 100% in each PFC, the current rating of the element in the circuit may be exceeded. Therefore, it is desirable to maintain each load factor at 100% or less. Therefore, the threshold value α is set to 50% or less, preferably 50%. That is, the threshold value α may be less than or equal to 1/2, preferably 1/2 of the load factor R that gives the highest power factor or efficiency in the entire PFC 20A and 20B.

The cumulative difference acquisition unit 45 includes a timekeeping means and acquires a difference value Td obtained by subtracting the cumulative value Tb of the stop time of the PFC 20B by the ON / OFF signal SPb from the cumulative value Ta of the stop time of the PFC 20A by the ON / OFF signal SPA. .. The cumulative difference acquisition unit 45 may acquire the difference value Td by subtracting the cumulative stop time of the PFC 20B from the cumulative stop time of the PFC 20A as described above, or subtracting the cumulative operation time of the PFC 20A from the cumulative operation time of the PFC 20B. You may get it.

When the difference value Td (= Ta-Tb) exceeds a predetermined time in the positive direction, the switching unit 46 causes the operation command unit 44 to operate the PFC 20A and stop the PFC 20B. On the other hand, when the difference value Td (= Ta-Tb) exceeds the predetermined time in the negative direction (that is, when Tb-Ta exceeds the predetermined time in the positive direction), the switching unit 46 sends the operation command unit 44 to the PFC20A. Is stopped and the PFC 20B is operated. As a result, the stop times of the PFCs 20A and 20B are equalized, that is, the operating times are equalized, and the lifespans of both are averaged. Therefore, the situation where one of the PFCs 20A and 20B reaches the end of its life earlier than the other is prevented, and the life of the LED lighting circuit 1 as a whole is extended.

As described above, the LED lighting circuit 1 of the present invention uses the PFC 20A and 20B to which the rectified output of the AC power supply AC is input and the output voltage of the PFC 20A or 20B as a voltage source, and uses a DC current corresponding to the dimming signal SDa as an LED. A DC / DC converter 30A that supplies the array 2A, a DC / DC converter 30B that supplies a direct current corresponding to the dimming signal SDb using the output voltage of the PFC 20A or 20B as a voltage source, and a central control unit 40. Be prepared. The central control unit 40 outputs a dimming command unit 42 that outputs dimming signals SDa and SDb to the DC / DC converters 30A and 30B, respectively, and the total maximum output of the DC / DC converters 30A and 30B based on the dimming signals SDa and SDb. A load factor calculation unit 43 that calculates the load factor R, which is the ratio of the total dimming output power Pdim to the power Pmax, and an operation command unit 44 that stops one of the PFC 20A and 20B when the load factor R is equal to or less than the threshold value α. Have.

In this way, at the time of low dimming, one of the PFCs 20A and 20B is stopped and the independent operation is applied, so that the operating PFC can operate closer to the optimum design point by increasing the load factor. Therefore, in the two-system output LED lighting circuit 1 and the LED lighting device 3, it is possible to maintain a high power factor and efficiency even at a light load such as low dimming.

<Second embodiment>
In the first embodiment, the configuration is shown in which the system A and the system B have the same maximum output power, and the PFC to be stopped is determined based on the cumulative stop time. On the other hand, in the present embodiment, the configuration is shown in which the system A and the system B have different maximum output powers, and the stopped PFC is based on the individual load factor of one PFC when operating independently.

FIG. 2 shows a block diagram of the LED lighting circuit 1 of the present embodiment and the LED lighting device 3 including the LED lighting circuit 1. It is assumed that the configuration of the central control unit 40 and the settings of the maximum output power Pa and Pb are different between the present embodiment and the first embodiment, and the maximum output power Pa is higher than the maximum output power Pb. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The central control unit 40 includes a dimming input unit 41, a dimming command unit 42, a load factor calculation unit 43, an operation command unit 44, and a selection unit 47. The dimming command unit 42, the load factor calculation unit 43, the operation command unit 44, and the selection unit 47 form a part of the CPU and are connected to each other and in a manner capable of transferring data to and from the memory. The load factor calculation unit 43 calculates the load factor R = Pdim / Pmax = (Pa × Da + Pb × Db) / (Pa + Pb). Then, when the load factor R is equal to or less than the threshold value α (for example, 50%), the operation command unit 44 stops one of the PFCs 20A and 20B and applies the independent operation.

The selection unit 47 calculates the individual load factor Rb, which is the ratio of the maximum output power Pb of the system B to the total dimming output power Pdim. When the individual load factor Rb is equal to or less than a predetermined value β (for example, 100%), the selection unit 47 selects the PFC 20B as the PFC that operates independently (in other words, selects it as the PFC that stops the PFC 20A). On the other hand, when the individual load factor Rb exceeds a predetermined value β (100%), the selection unit 47 selects the PFC 20A as the PFC that operates independently (in other words, selects it as the PFC that stops the PFC 20B). The selection unit 47 makes the above selection at the time of starting the LED lighting circuit 1 and each time at least one of the dimming rates Da and Db is changed, and turns ON / according to the selection result (when the independent operation is performed). The OFF signals SPA and SPb are output to the operation command unit 44. The predetermined value β may be about twice the threshold value α.

For example, when α = 50%, β = 100%, Pa = 100W, Pb = 50W, Da = 20%, Db = 50%, the total maximum output power Pmax = Pa + Pb = 150W, the total dimming output power Pdim = Pa × Da + Pb × Db = 45W. Since the load factor R = Pdim / Pmax = 30% <α, the independent operation is applied. Here, since the individual load factor Rb = Pdim / Pb = 90% ≦ β, the selection unit 47 selects the PFC 20B as the PFC for operating independently. If the PFC 20A operates independently, the individual load factor Ra = Pdim / Pa = 45% of the system A.
Further, as another example, when α = 50%, β = 100%, Pa = 100W, Pb = 50W, Da = 50%, Db = 20%, the total maximum output power Pmax = Pa + Pb = 150W, total adjustment. The optical output power Pdim = Pa × Da + Pb × Db = 60W. Since the load factor R = Pdim / Pmax = 40% <α, the independent operation is applied. Here, since the individual load factor Rb = Pdim / Pb = 120%> β, the selection unit 47 selects the PFC 20A as the PFC for operating independently. In this case, the individual load factor Ra = Pdim / Pa = 60%.

As described above, according to the LED lighting circuit 1 of the present embodiment, the maximum output power of the PFC 20A corresponds to the maximum output power Pa of the DC / DC converter 30A, and the maximum output power of the PFC 20B is the maximum output of the DC / DC converter 30B. When Pa> Pb corresponding to the electric power Pb, the selection unit 47 has an individual load factor Rb which is a ratio of the total dimming output power Pdim to the maximum output power Pb is a predetermined value β (for example, 100%) or less. In some cases, the operation command unit 44 stops the PFC 20A to operate the PFC 20B, and when the individual load factor Rb exceeds a predetermined value β, the operation command unit 44 stops the PFC 20B to operate the PFC 20A. As a result, the individual load factor of each of the PFCs 20A and 20B is maximized within the range of the maximum output power or less, and a high power factor and efficiency can be obtained for the LED lighting circuit 1 as a whole.

<Third embodiment>
In the first embodiment, a fixed threshold value α and a load factor calculation formula are used, but in the present embodiment, a variable threshold value α or a load factor calculation formula is used according to the AC power supply voltage. Is shown. In this embodiment, even if the output power is the same, the PFC is in a relatively light load state when the input voltage is relatively high, and the above is described when the input voltage is relatively high. The PFC is positively operated independently.

FIG. 3 shows a block diagram of the LED lighting circuit 1 of the present embodiment and the LED lighting device 3 including the LED lighting circuit 1. The configuration of the central control unit 40 is different between the present embodiment and the first embodiment. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The central control unit 40 further includes a voltage detection unit 48 in addition to a dimming input unit 41, a dimming command unit 42, a load factor calculation unit 43, an operation command unit 44, a cumulative difference acquisition unit 45, and a switching unit 46. The voltage detection unit 48 detects the output voltage of the rectifier circuit 10B (or 10A) and detects the power supply voltage Vac of the AC power supply AC. The voltage detection unit 48 outputs a detection signal corresponding to the detected power supply voltage Vac to the operation command unit 44 or the load factor calculation unit 43.

When the detection signal is input to the operation command unit 44, the operation command unit 44 raises / lowers the threshold value α with respect to the increase / decrease of the power supply voltage Vac indicated by the detection signal. That is, when the power supply voltage Vac is relatively low (for example, AC100V), a relatively low threshold value α is applied and parallel operation by both PFC 20A and 20B is positively performed. On the other hand, when the power supply voltage Vac is relatively high (for example, AC200V), a relatively high threshold value α is applied and the independent operation by the PFC 20A or 20B is positively performed.

When the detection signal is input to the load factor calculation unit 43, the load factor calculation unit 43 changes the weighting of the calculation of the load factor R according to the power supply voltage Vac indicated by the detection signal. That is, for the same output power, the load factor R1 when the power supply voltage Vac is relatively low (for example, AC100V) is higher than the load factor R2 when the power supply voltage Vac is relatively high (for example, AC200V). The calculation formula is set so as to be. Therefore, when the power supply voltage Vac is relatively high with respect to the same threshold value α, the independent operation of the PFC 20A or 20B is applied at higher dimming rates Da and Db.

The commercial power supply has power supply voltages of 100V, 110V, 115V, 120V, 200V, 220V, 230V, 240V, 242V, 265V and the like (all are nominal values) in Japan and overseas. Macroscopically, the threshold value α or the load factor calculation formula is changed according to these power supply voltages according to the above-described embodiment, but microscopically, the threshold value α or the load factor is changed according to the power supply voltage fluctuation even at the same power supply voltage Vac. The formula can be modified according to the above aspects.

As described above, in the LED lighting circuit 1 of the present embodiment, the central control unit 40 further includes a voltage detection unit 48 for detecting the power supply voltage Vac, and the operation command unit 44 has a threshold value α for an increase in the power supply voltage Vac. Is configured to raise. Alternatively, the load factor calculation unit 43 calculates so that the load factor R is relatively low when the power supply voltage Vac is relatively high as compared with the case where the power supply voltage Vac is relatively low. As a result, in the central control unit 30, the light load state is overestimated with respect to the increase in the power supply voltage Vac due to the difference or fluctuation of the AC power supply AC, and the transition condition for the independent operation of the PFC 20A or 20B is set. Optimized.

<Fourth Embodiment>
In the first embodiment, the high potential side wirings Ha and Hb are connected by the wiring Lh, but in the present embodiment, the high potential side wirings Ha and Hb are connected by the switch element.

FIG. 4 shows a block diagram of the LED lighting circuit 1 of the present embodiment and the LED lighting device 3 including the LED lighting circuit 1. The present embodiment and the first embodiment differ only in the connection configuration between the high potential side wiring Ha and the high potential side wiring Hb. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The central control unit 40 is the central control unit 40 in any of the first to third embodiments.

In the present embodiment, a pair of antiparallel diodes 51 and 52 are provided between the high potential side wiring Ha and the high potential side wiring Hb. The pair of antiparallel diodes are two diodes in which the cathode of one diode is connected to the anode of the other diode and the anode of one diode is connected to the cathode of the other diode. In this embodiment, two diodes 51 and 52 are shown as a pair of antiparallel diodes that are switch elements, but the pair of antiparallel diodes may be composed of two Zener diodes.

It is assumed that the output voltage during operation of the PFC 20A and the output voltage during operation of the PFC 20B are substantially equal to each other. Generally, the forward voltage of a power diode such as the diodes 51 and 52 is about 1 V. Therefore, if the difference between the output voltage during operation of the PFC 20A and the output voltage during operation of the PFC 20B is substantially equal and less than about 1 V. Both the diodes 51 and 52 are turned off. On the other hand, when the PFC 20A operates and the PFC 20B stops, only the diode 51 is turned on, and the output of the PFC 20A is supplied to the DC / DC converters 30A and 30B. When the PFC 20A stops and the PFC 20B operates, only the diode 52 is turned on, and the output of the PFC 20B is supplied to the DC / DC converters 30A and 30B. This provides a substantially continuous switch between parallel and independent operation of the PFC.

As described above, in the LED lighting circuit 1 of the present embodiment, the output voltage during operation of PFC20A and the output voltage during operation of PFC20B are substantially equal, and the low potential output end of PFC20A and the low potential output end of PFC20B are substantially equal. Is connected, and a pair of antiparallel diodes 51 and 52 connected between the high potential output end of the PFC 20A and the high potential output end of the PFC 20B are provided. As a result, during the parallel operation of the PFCs 20A and 20B, both the diodes 51 and 52 are turned off, and the converter circuit 5A and the converter circuit 5B become independent. Therefore, for example, when the maximum output powers of the systems A and B are different from each other, the design consistency in the parallel operation is maintained.

<Fifth Embodiment>
In the first embodiment, the smoothing capacitors 24A and 24B are shared by the PFCs 20A and 20B and also by the DC / DC converters 30A and 30B. In this embodiment, the smoothing capacitors 24A and 24B are shared by the PFCs 20A and 20B, but are not shared between the DC / DC converters 30A and 30B.

FIG. 5 shows a block diagram of the LED lighting circuit 1 of the present embodiment and the LED lighting device 3 including the LED lighting circuit 1. The connection configuration of the converter circuit 5A and the converter circuit 5B is different between the present embodiment and the first embodiment. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The central control unit 40 is the central control unit 40 in any of the first to third embodiments.

In the LED lighting circuit 1 of the present embodiment, the diodes 56 and 57 are provided in a configuration in which the wiring Lg is connected and the wiring Lh is not connected. The anode and cathode of the diode 56 are connected to the anode of the diode 23A and the cathode of the diode 23B, respectively, and the anode and cathode of the diode 57 are connected to the anode of the diode 23B and the cathode of the diode 23A, respectively.

It is assumed that the PFC 20A (switching element 21A) is stopped and the PFC 20B operates independently. The switching output of the switching unit of the PFC 20B is charged to the smoothing capacitor 24B via the diode 23B and to the smoothing capacitor 24A via the diode 57. The same applies when the PFC 20B (switching element 21B) is stopped and the PFC 20A operates independently. That is, the switching output of the switching unit of the PFC 20A is charged to the smoothing capacitor 24A via the diode 23A and to the smoothing capacitor 24B via the diode 56. In either case, the DC / DC converter 30A operates using only the smoothing capacitor 24A as a voltage source, and the DC / DC converter 30B operates using only the smoothing capacitor 24B as a voltage source. This configuration provides a substantially continuous switch between parallel and independent operation of the PFC.

As described above, in the LED lighting circuit 1 of the present embodiment, the low potential side node of the smoothing capacitor 24A and the low potential side node of the smoothing capacitor 24B are connected, and this is between the anode of the diode 23A and the cathode of the diode 23B. A diode 56 connected with the direction as the rectifying direction and a diode 57 connected with this direction as the rectifying direction are provided between the anode of the diode 23B and the cathode of the diode 23A.

As a result, the smoothing capacitor 24A is not connected to the DC / DC converter 30B, and the smoothing capacitor 24B is not connected to the DC / DC converter 30A. Therefore, the independence of the smoothing capacitor 24A and the DC / DC converter 30A and the smoothing capacitor 24B and the DC / DC converter 30B can be obtained. Therefore, for example, in a configuration in which smoothing capacitors 24A and 24B having different capacities are adopted in DC / DC converters 30A and 30B having different maximum output powers, even when the PFC 20A or 20B is operated independently, the smoothing capacitors 24A and 24B and DC / The design consistency of each of the DC converters 30A and 30B is maintained. Further, from the viewpoint of the PFC 20A or 20B, since the smoothing capacitors 24A and 24B are maintained in parallel even if one of them is stopped, an increase in the output ripple is avoided even when the PFC is operating alone.

<Sixth Embodiment>
In the first embodiment, the smoothing capacitors 24A and 24B are shared by the PFCs 20A and 20B and also by the DC / DC converters 30A and 30B. In this embodiment, the smoothing capacitors 24A and 24B are shared by the DC / DC converters 30A and 30B, but are not shared by the PFC 20A and 20B.

FIG. 6 shows a block diagram of the LED lighting circuit 1 of the present embodiment and the LED lighting device 3 including the LED lighting circuit 1. The connection configuration of the converter circuit 5A and the converter circuit 5B is different between the present embodiment and the first embodiment. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The central control unit 40 is the central control unit 40 shown in any of the first to third embodiments.

In the LED lighting circuit 1 of the present embodiment, the diodes 61 to 64 are provided in a configuration in which the wiring Lg is connected and the wiring Lh is not connected. The diodes 61 and 62 are inserted and connected to the wirings Ha and Hb with the initial current direction as the rectifying direction, respectively. The anode and cathode of the diode 63 are connected to the anode of the diode 61 and the cathode of the diode 62, respectively, and the anode and cathode of the diode 64 are connected to the anode of the diode 62 and the cathode of the diode 61, respectively.

When the PFC 20A is stopped and the PFC 20B operates, the smoothing capacitor 24B is charged by the operation of the PFC 20B, and the DC / DC converters 30A and 30B operate using the smoothing capacitor 24B as a voltage source. On the other hand, when the PFC 20B is stopped and the PFC 20A operates, the smoothing capacitor 24A is charged by the operation of the PFC 20A, and the DC / DC converters 30A and 30B operate using the smoothing capacitor 24A as a voltage source. In either case, the PFC 20A charges only the smoothing capacitor 24A, and the PFC 20B charges only the smoothing capacitor 24B. This configuration provides a substantially continuous switch between parallel and independent operation of the PFC.

As described above, in the LED lighting circuit 1 of the present embodiment, the low potential side node of the smoothing capacitor 24A and the low potential side node of the smoothing capacitor 24B are connected, and DC / DC / from the high potential side node of the smoothing capacitor 24A to the wiring Ha. The direction of the diode 61 inserted and connected with the direction of the DC converter 30A toward the high potential side input end as the rectification direction and the direction of the smoothing capacitor 24B from the high potential side node of the DC / DC converter 30B to the high potential side input end of the wiring Hb. A diode 62 inserted and connected with this direction as the rectifying direction, a diode 63 connected between the high potential side node of the smoothing capacitor 24A and the high potential side input end of the DC / DC converter 30B with this direction as the rectifying direction, and a smoothing capacitor. A diode 64 connected in this direction as a rectifying direction is provided between the high potential side node of 24B and the high potential side input end of the DC / DC converter 30A.

As a result, the smoothing capacitor 24A is not connected to the PFC20B, and the smoothing capacitor 24B is not connected to the PFC20A. Therefore, during the independent operation of the PFC, the smoothing capacitors included in the stopped PFC are completely de-energized, so that the life of each smoothing capacitor is expected to be extended. Further, since the life of the PFC tends to depend on the life of the smoothing capacitor (electrolytic capacitor), the cumulative value of the stop time of the PFC and the cumulative value of the non-energized time of the smoothing capacitor match, so that the first embodiment The above-mentioned accuracy of life averaging is improved.

<Modification example>
Although the preferred embodiments of the present invention have been shown above, the present invention can be transformed into various aspects as shown below, for example.

(1) Modification Regarding Selection of PFC to be Stopped In the first embodiment, the configuration in which the PFC to be stopped is switched according to the cumulative stop time is shown. On the other hand, in a lighting device set to turn on and off and dimming periodically or periodically as used in a road light, the PFC to be stopped may be alternately selected for each lighting time.

(2) Combination and Synthesis of Embodiments Although the first to sixth embodiments have been described as individual ones, some or all of the first to sixth embodiments may be combined with each other. .. For example, although the third embodiment has been described in relation to the first embodiment, the configuration including the voltage detection unit 48 of the third embodiment is also applicable to the second embodiment.

Further, as a synthesis of the fifth embodiment and the sixth embodiment, as shown in FIG. 7, it is possible to configure only the diodes 57, 62 and 63 of the diodes 56 to 64 to be connected. In this case, when the PFC 20A operates independently, only the smoothing capacitor 24A is charged, and the DC / DC converters 30A and 30B operate using the smoothing capacitor 24A as a voltage source. Further, when the PFC 20B is operated independently, the smoothing capacitors 24A and 24B are charged, the DC / DC converter 30A operates using only the smoothing capacitor 24A as a voltage source, and the DC / DC converter 30B operates using the smoothing capacitors 24A and 24B as a voltage source. To do. This connection configuration is useful when the smoothing capacitor 24A is to be used more positively than the smoothing capacitor 24B. As an inverting configuration (a configuration in which the system A and the system B are reversed), a configuration in which only the diodes 56, 61, and 64 of the diodes 56 to 64 are connected is also possible.

1 LED lighting circuit 2A, 2B LED array 3 LED lighting device 20A, 20B PFC (power factor improvement circuit)
21A, 21B switching element (switching part)
22A, 22B inductor (switching part)
23A, 23B Diode 24A, 24B Smoothing capacitor 30A, 30B DC / DC converter 40 Central control unit 42 Dimming command unit 43 Load factor calculation unit 44 Operation command unit 45 Cumulative difference acquisition unit 46 Switching unit 47 Selection unit 48 Voltage detection unit 51 , 52, 56, 57, 61-64 diodes

Claims (10)

It is an LED lighting circuit
The first power factor improvement circuit to which the rectified output of the AC power supply is input,
A second power factor improving circuit to which the rectified output of the AC power supply is input, and
A first DC / DC converter that supplies a direct current corresponding to the first dimming signal to the first LED array using the output voltage of the first or second power factor improving circuit as a voltage source.
A second DC / DC converter that supplies a direct current corresponding to the second dimming signal to the second LED array using the output voltage of the first or second power factor improving circuit as a voltage source.
A dimming command unit that outputs the first and second dimming signals to the first and second DC / DC converters, respectively, and the first and second dimming signals based on the first and second dimming signals. The load factor calculation unit that calculates the load factor, which is the ratio of the total dimming output power to the total maximum output power of the DC / DC converter, and the first and second power factors when the load factor is equal to or less than the threshold value. An LED lighting circuit including a central control unit including an operation command unit that stops one of the improvement circuits and applies independent operation. The central control unit acquires a difference value obtained by subtracting the cumulative value of the stop time of the second power factor improvement circuit from the cumulative value of the stop time of the first power factor improvement circuit, and the cumulative difference acquisition unit. When the difference value exceeds a predetermined time in the positive direction, the operation command unit operates the first power factor improvement circuit and stops the second power factor improvement circuit, and the difference value is in the negative direction. The LED lighting circuit according to claim 1, further comprising a switching unit in which the operation command unit stops the first power factor improving circuit and operates the second power factor improving circuit when the predetermined time is exceeded. .. The maximum output power of the first power factor improving circuit corresponds to the first maximum output power of the first DC / DC converter, and the maximum output power of the second power factor improving circuit corresponds to the second DC / DC. Corresponding to the second maximum output power of the converter, the first maximum output power is higher than the second maximum output power.
When the central control unit has an individual load factor which is a ratio of the total dimming output power to the second maximum output power to a predetermined value or less, the operation command unit is provided with the first power factor improving circuit. The second power factor improving circuit is operated by stopping, and when the individual load factor exceeds the predetermined value, the operation command unit stops the second power factor improving circuit to operate the first power factor. The LED lighting circuit according to claim 1, further comprising a selection unit for operating a power factor improving circuit. The central control unit further includes a voltage detection unit that detects the power supply voltage of the AC power source.
The LED lighting circuit according to any one of claims 1 to 3, wherein the operation command unit is configured to raise the threshold value with respect to an increase in the power supply voltage. The central control unit further includes a voltage detection unit that detects the power supply voltage of the AC power source.
Any of claims 1 to 3, wherein the load factor calculation unit calculates so that the load factor becomes relatively low when the power supply voltage is relatively high as compared with the case where the power supply voltage is relatively low. The LED lighting circuit according to one item. The low potential output end of the first power factor improving circuit and the low potential output end of the second power factor improving circuit are connected, and the high potential output end of the first power factor improving circuit and the second power factor improving circuit are connected. The LED lighting circuit according to any one of claims 1 to 5, wherein the high potential output end of the power factor improving circuit is connected. The output voltage during operation of the first power factor improving circuit and the output voltage during operation of the second power factor improving circuit are substantially equal to each other with the low potential output end of the first power factor improving circuit. The low potential output end of the second power factor improving circuit is connected, and the high potential output end of the first power factor improving circuit is connected to the high potential output end of the second power factor improving circuit. The LED lighting circuit according to any one of claims 1 to 5, further comprising a pair of antiparallel diodes. The first power factor improving circuit charges the first switching unit that switches the input voltage, the first diode that rectifies the switching output of the first switching unit, and the rectified output of the first diode. Has a first smoothing capacitor
The second power factor improving circuit charges the second switching unit that switches the input voltage, the second diode that rectifies the switching output of the second switching unit, and the rectified output of the second diode. Has a second smoothing capacitor
The low potential side node of the first smoothing capacitor and the low potential side node of the second smoothing capacitor are connected.
A third diode connected between the anode of the first diode and the cathode of the second diode with the direction from the anode of the first diode to the cathode of the second diode as the rectifying direction. ,
A fourth diode connected between the anode of the second diode and the cathode of the first diode with the direction from the anode of the second diode to the cathode of the first diode as the rectifying direction. The LED lighting circuit according to any one of claims 1 to 5, further comprising. The first power factor improving circuit includes a first smoothing capacitor between the output ends.
The second power factor improving circuit includes a second smoothing capacitor between the output ends.
The low potential side node of the first smoothing capacitor and the low potential side node of the second smoothing capacitor are connected.
In the wiring between the high potential side node of the first smoothing capacitor and the high potential side input end of the first DC / DC converter, the high potential side node of the first smoothing capacitor to the first DC / A third diode inserted and connected with the direction of the high potential side input end of the DC converter as the rectification direction,
In the wiring between the high potential side node of the second smoothing capacitor and the high potential side input end of the second DC / DC converter, the high potential side node of the second smoothing capacitor to the second DC / A fourth diode inserted and connected with the direction of the high potential side input end of the DC converter as the rectification direction,
Between the high potential side node of the first smoothing capacitor and the high potential side input end of the first DC / DC converter, from the high potential side node of the first smoothing capacitor to the first DC / DC converter. A fifth diode connected with the direction of the input end on the high potential side as the rectification direction,
Between the high potential side node of the second smoothing capacitor and the high potential side input end of the first DC / DC converter, from the high potential side node of the second smoothing capacitor to the first DC / DC converter. The LED lighting circuit according to any one of claims 1 to 5, further comprising a sixth diode connected with the direction of the high potential side input end of the above as a rectifying direction. An LED lighting device comprising the LED lighting circuit according to any one of claims 1 to 9 and the first and second LED arrays.

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