Switching power supply device and control device

Abstract

To provide a switching power supply device and a control device that reduce noise generated from an electronic device in a configuration using a buck converter.SOLUTION: A switching power supply device includes: a buck converter 20 including a switching element 34, a coil 35, an output terminal 38 connected to the other end of the coil, a rectifying element 36, and a capacitor 37, of which one end is connected to the output terminal and the other end is connected to a ground terminal 39; and a control unit 21 for controlling switching operations of the switching element. The control unit includes: a valley point detection unit for detecting a valley point of a resonance signal of a voltage generated at both ends of the switching element after all magnetic energy of the coil is released; a valley point count unit for counting the number of valley points; and a timing control unit for controlling a timing of turning on the switching element 34 according to a count result of the valley points of the resonance signal and a load information level of an external device to be delayed until the load information level indicates a light load.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a switching power supply device and a control device. [Background technology]

[0002] There is known a technique for controlling the operation of a lighting device using a conversion circuit including a switching element. Patent Document 1 describes a technique that can achieve both a reduction in the number of switching elements and an improvement in the degree of freedom in dimming. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-16680 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, lighting equipment is required to reduce the average noise level to comply with the international standard CISPRJ 15:2017. When operating lighting equipment using a buck converter that operates at a fixed frequency, it is difficult to implement noise countermeasures. There is a demand for technology to reduce noise in lighting equipment using a configuration that uses a buck converter.

[0005] An object of the present disclosure is to provide a switching power supply device and a control device that are capable of reducing noise generated from an electronic device in a configuration using a buck converter. [Means for solving the problem]

[0006] The switching power supply device according to the present disclosure includes a buck converter including an input terminal, a switching element having a first terminal electrically connected to the input terminal, a coil having one end electrically connected to a second terminal of the switching element, an output terminal electrically connected to the other end of the coil, a rectifying element having a cathode electrically connected between the switching element and the coil and an anode electrically connected to a reference potential, and a capacitor having one end electrically connected to the output terminal and the other end electrically connected to the reference potential, and a control unit for controlling a switching operation of the switching element, wherein the control unit generates magnetic energy by flowing a current through the coil when the switching element is on. a valley point detection unit that stores magnetic energy in the coil and releases the magnetic energy stored in the coil when the switching element is off, and detects valley points of a resonant signal of a voltage generated across both ends of the switching element after all of the magnetic energy of the coil has been released; a valley point counting unit that counts the number of valley points based on a detection result of the valley point detection unit; and a timing control unit that acquires a load information level from an external device and controls a timing for turning on the switching element in accordance with a count result of the valley points of the resonant signal by the valley point counting unit and the load information level, wherein the timing control unit delays the timing for turning on the switching element as the load information level indicates a lighter load.

[0007] In the switching power supply device disclosed herein, the control unit includes a time measurement unit that measures the time from when the switching element is turned on until the valley point detection unit detects a first valley point of the resonant signal, and the timing control unit turns on the switching element at a timing when the count number of the valley point counting unit is a first count number if the measurement result by the time measurement unit is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting unit is a second count number less than the first count number if the measurement result by the time measurement unit exceeds a second time that is longer than the first time.

[0008] In the switching power supply device according to the present disclosure, the timing control section turns on the switching element at a timing at which the first count number and the second count number are increased as the load information level indicates a lighter load.

[0009] In the switching power supply device according to the present disclosure, the control unit has a control terminal pulled up to a predetermined voltage, and the timing control unit controls the timing for turning on the switching element in accordance with the measured value of the voltage of the control terminal.

[0010] In the switching power supply device according to the present disclosure, the load information level is at least one of an output current of a lighting device and a dimming signal indicating illuminance.

[0011] A switching power supply device according to the present disclosure includes a buck converter including an input terminal, a switching element having a first terminal electrically connected to the input terminal, a coil having one end electrically connected to a second terminal of the switching element, an output terminal electrically connected to the other end of the coil, a rectifying element having a cathode electrically connected between the switching element and the coil and an anode electrically connected to a reference potential, and a capacitor having one end electrically connected to the output terminal and the other end electrically connected to the reference potential, and a control unit that controls a switching operation of the switching element, wherein the control unit stores magnetic energy by passing a current through the coil when the switching element is on, releases the magnetic energy stored in the coil when the switching element is off, and generates a magnetic current between both ends of the switching element after all the magnetic energy in the coil has been released. a valley point detection unit that detects valley points of a resonance signal of a voltage to be inputted to the switching element, a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit, a time measurement unit that measures a time from when the switching element is turned on until the valley point detection unit detects a first valley point of the resonance signal, and a timing control unit that controls a timing for turning on the switching element in accordance with a count result of the valley points of the resonance signal by the valley point counting unit and a measurement result of the time by the time measurement unit, wherein the timing control unit turns on the switching element at a timing when the count number of the valley point counting unit is a first count number if the measurement result by the time measurement unit is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting unit is a second count number less than the first count number if the measurement result by the time measurement unit exceeds a second time longer than the first time.

[0012] A switching power supply device according to the present disclosure includes a buck converter including an input terminal, a switching element having a first terminal electrically connected to the input terminal, a coil having one end electrically connected to a second terminal of the switching element, an output terminal electrically connected to the other end of the coil, a rectifying element having a cathode electrically connected between the switching element and the coil and an anode electrically connected to a reference potential, and a capacitor having one end electrically connected to the output terminal and the other end electrically connected to the reference potential, and a control unit that controls a switching operation of the switching element, the switching element stores magnetic energy by passing a current through the coil when the switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and includes a valley point detection unit that detects valley points of a resonant signal of a voltage generated across both ends of the switching element after all the magnetic energy of the coil has been released, a valley point counting unit that counts the number of valley points based on a detection result of the valley point detection unit, a control terminal pulled up to a predetermined voltage, and a timing control unit that controls the timing of turning on the switching element in accordance with the measured value of the voltage of the control terminal.

[0013] The control device of the present disclosure stores magnetic energy by passing a current through a coil when a switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and includes a valley point detection unit that detects valley points of a resonant signal of a voltage generated across both ends of the switching element after all the magnetic energy of the coil has been released, a valley point counting unit that counts the number of valley points based on the detection result of the valley point detection unit, and a timing control unit that acquires a load information level from an external device and controls the timing of turning on the switching element in accordance with the counting result of the valley points of the resonant signal by the valley point counting unit and the load information level, and the timing control unit delays the timing of turning on the switching element the more the load information level indicates a lighter load.

[0014] A control device according to the present disclosure stores magnetic energy by passing a current through a coil when a switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and includes a valley point detection unit that detects valley points of a resonant signal of a voltage generated across both ends of the switching element after all of the magnetic energy of the coil has been released, a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit, a time measurement unit that measures the time until the valley point detection unit detects a first valley point of the resonant signal after the switching element is turned on, and a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit. and a timing control unit that controls the timing of turning on the switching element in accordance with a counting result of valley points of the resonance signal by a counting unit and a result of time measurement by the time measurement unit, wherein the timing control unit turns on the switching element at a timing when the count number of the valley point counting unit is a first count number if the measurement result by the time measurement unit is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting unit is a second count number less than the first count number if the measurement result by the time measurement unit exceeds a second time that is longer than the first time.

[0015] The control device of the present disclosure stores magnetic energy by passing a current through a coil when a switching element is on, and releases the magnetic energy stored in the coil when the switching element is off.The control device also includes a valley point detection unit that detects valley points of a resonant signal of a voltage generated across both ends of the switching element after all the magnetic energy in the coil has been released, a valley point counting unit that counts the number of valley points based on the detection result of the valley point detection unit, and a timing control unit that controls the timing of turning on the switching element in accordance with the measured value of the voltage of a control terminal pulled up to a predetermined voltage. Effect of the Invention

[0016] According to the present disclosure, it is possible to reduce noise generated from an electronic device by using a configuration that uses a buck converter. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a circuit diagram showing a configuration example of a lighting device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating an example of the configuration of a control unit according to the first embodiment. [Diagram 3] FIG. 3 is a diagram for explaining a resonance signal generated across both ends of a switching element. [Figure 4] FIG. 4 is a diagram for explaining a method for controlling the timing of turning on the switching element according to the first embodiment. [Diagram 5] FIG. 5 is a block diagram showing an example of the configuration of a control unit according to the second embodiment. [Figure 6] FIG. 6 is a diagram for explaining a method for controlling the timing of turning on a switching element according to the second embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of the configuration of a control unit according to the third embodiment. [Figure 8] FIG. 8 is a diagram for explaining a method for controlling the timing of turning on a switching element according to the third embodiment. [Figure 9] FIG. 9 is a diagram for explaining a method of controlling the timing of turning on a switching element according to the fourth embodiment. [Figure 10] FIG. 10 is a table for explaining a method of controlling the switching element according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited to this embodiment, and in the following embodiments, the same components are designated by the same reference numerals, and duplicated descriptions will be omitted.

[0019] [Embodiment] An example of the configuration of a lighting device according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram showing an example of the configuration of a lighting device according to an embodiment.

[0020] 1, the lighting device 1 includes a switching power supply device 10, a PFC (Power Factor Correction) circuit unit 11, and a light-emitting unit 12. The lighting device 1 is configured to receive an AC voltage from an AC power supply 2 to cause the light-emitting unit 12 to emit light. The AC power supply 2 is, for example, a system power supply, but is not limited to this.

[0021] The switching power supply device 10 includes a buck converter 20 and a control unit 21.

[0022] The buck converter 20 includes an input terminal 31, a ground terminal 32, a capacitor 33, a switching element 34, a coil 35, a rectifying element 36, a capacitor 37, an output terminal 38, and a ground terminal 39. In this embodiment, the buck converter 20 is a quasi-resonant buck converter.

[0023] The PFC circuit unit 11 is electrically connected to the input terminal 31 and the ground terminal 32. A predetermined output voltage is input to the input terminal 31 from the PFC circuit unit 11.

[0024] The ground terminal 32 is connected to a reference potential, which may be, but is not limited to, a ground potential.

[0025] One end of the capacitor 33 is electrically connected to the input terminal 31. The other end of the capacitor 33 is electrically connected to the ground terminal 32. The capacitor 33 smoothes the output voltage input from the PFC circuit unit 11.

[0026] The switching element 34 is a semiconductor element such as a metal-oxide-semiconductor field-effect transistor (MOSFET). The switching element 34 has a drain terminal electrically connected to the input terminal 31. The drain terminal is also called a first terminal. The switching element 34 has a source terminal electrically connected to one end of the coil 35. The source terminal is also called a second terminal. A control signal is input from the control unit 21 to a gate terminal of the switching element 34. The gate terminal is also called a third terminal. That is, the switching element 34 is installed on the high side. The switching element 34 may be a silicon power device, a GaN power device, a SiC power device, an IGBT (Insulated Gate Bipolar Transistor), or the like.

[0027] One end of the coil 35 is electrically connected to the source terminal of the switching element 34. The other end of the coil 35 is electrically connected to the output terminal 38.

[0028] The cathode of the rectifying element 36 is electrically connected between the switching element 34 and the coil 35. The anode of the rectifying element 36 is electrically connected to a reference potential.

[0029] The capacitor 37 has one end electrically connected between the coil 35 and the output terminal 38. The other end of the capacitor 37 is electrically connected to a reference potential. The capacitor 37 smoothes the output voltage. The capacitor 37 supplies the smoothed output voltage to the light-emitting unit 12.

[0030] The light-emitting unit 12 is electrically connected to the output terminal 38 and the ground terminal 39. The light-emitting unit 12 includes, for example, a plurality of LED (Light Emitting Diode) elements connected in series. The light-emitting unit 12 may be composed of one LED element. The output terminal 38 is electrically connected to the anode of the LED element of the light-emitting unit 12. The ground terminal 39 is electrically connected to the cathode of the LED element of the light-emitting unit 12. The light-emitting unit 12 is an example of an external device in the present disclosure. In the present disclosure, the external device is not limited to the light-emitting unit 12 and may be another device.

[0031] The ground terminal 39 is connected to a reference potential, which may be, but is not limited to, a ground potential.

[0032] The PFC circuit unit 11 includes a rectifier circuit 41 , a capacitor 42 , a coil 43 , a switching element 44 , and a rectifier element 45 .

[0033] The rectifier circuit 41 is, for example, a bridge diode including four or six diodes (not shown). The rectifier circuit 41 is configured to full-wave rectify the AC voltage output from the AC power supply 2 and output the full-wave rectified voltage to the capacitor 42. The rectifier circuit 41 has a bridge diode whose cathode side is electrically connected to one end of the coil 43. The rectifier circuit 41 has a bridge diode whose anode side is electrically connected to the ground terminal 32 of the buck converter 20.

[0034] The capacitor 42 has one end electrically connected between the rectifier circuit 41 and the coil 43. The other end of the capacitor 42 is electrically connected to a reference potential. The capacitor 42 smoothes the output voltage from the rectifier circuit 41.

[0035] One end of the coil 43 is electrically connected to the cathode side of the diode of the rectifier circuit 41. The other end of the coil 43 is electrically connected to the anode of the rectifier element 45.

[0036] The switching element 44 has a drain terminal electrically connected between the coil 43 and the rectifier element 45. The switching element 44 has a source terminal electrically connected to a reference potential. The switching element 44 is configured so that a control signal is input from the control unit 21 to a gate terminal.

[0037] The rectifying element 45 is configured such that the anode is electrically connected to the other end of the coil 43. The rectifying element 45 has a cathode electrically connected to the input terminal 31 of the buck converter 20.

[0038] The control unit 21 controls the switching operations of the switching element 34 of the buck converter 20 and the switching element 44 of the PFC circuit unit 11. The control unit 21 controls the switching operations of the switching element 34 and the switching element 44, for example, by outputting control signals to gate terminals of the switching element 34 and the switching element 44.

[0039] The control unit 21 is realized, for example, by a central processing unit (CPU) or a micro processing unit (MPU) executing a program stored in a storage unit (not shown) using a RAM or the like as a working area. The control unit 21 may be realized, for example, by an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control unit 21 may be realized by a combination of hardware and software.

[0040] In the embodiment of the present disclosure, the control unit 21 turns off the switching element 34 and releases magnetic energy from the coil 35, thereby generating a resonance signal caused by the parasitic capacitance of the switching element 34 and the inductance of the coil 35. After the switching element 34 and the coil 35 generate the resonance signal, the control unit 21 controls the timing to turn on the switching element 34, thereby reducing noise of the LED elements of the light-emitting unit 12. The control unit 21 controls the timing to turn on the switching element 34 according to the timing of the valley point of the resonance signal and the level of the dimming signal indicating load information of the LED elements of the light-emitting unit 12.

[0041] An example of the configuration of the control unit according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram showing an example of the configuration of the control unit according to the first embodiment.

[0042] As shown in FIG. 2, the control unit 21 includes a switching control unit 51, a valley point detection unit 52, a valley point counting unit 53, and a timing control unit .

[0043] The switching control unit 51 controls the switching between on and off of the switching element 34. The switching control unit 51 controls the switching between on and off of the switching element 44.

[0044] 3 is a diagram for explaining a resonant signal generated across both ends of the switching element 34. FIG 3 shows a voltage waveform between the drain and source of the switching element 34.

[0045] 3, the switching control unit 51 outputs a control signal to the switching element 34 to turn on the switching element 34. A drain current flows through the switching element 34. When the drain current flows through the switching element 34, magnetic energy is accumulated in the coil 35.

[0046] 3, the switching control unit 51 stops outputting the control signal to the switching element 34 to turn off the switching element 34. This causes no drain current to flow through the switching element 34. When no drain current flows through the switching element 34, the magnetic energy stored in the coil 35 is released.

[0047] 3, all of the magnetic energy is discharged from the coil 35. When all of the magnetic energy is discharged from the coil 35, resonance occurs between the drain and source of the switching element 34. The resonance between the drain and source of the switching element 34 is caused by the parasitic capacitance of the switching element 34 and the inductance of the coil 35.

[0048] Timing t3 to timing t8 are the period during which resonance occurs. Timing t4 is the timing when the first valley point of the resonance signal indicating resonance is detected. Timing t5 is the timing when the second valley point of the resonance signal is detected. Timing t6 is the timing when the third valley point of the resonance signal is detected. Timing t7 is the timing when the fourth valley point of the resonance signal is detected. Timing t8 is the timing when the fifth valley point of the resonance signal is detected.

[0049] The valley point detection unit 52 detects a valley point of a resonant signal of a voltage generated across the switching element 34. When the switching element 34 is off, the valley point detection unit 52 releases the magnetic energy stored in the coil 35, and detects a valley point of a resonant signal of a voltage generated across the switching element 34 after all the magnetic energy of the coil 35 is released. Specifically, the valley point detection unit 52 detects valley points at timings t4, t5, t6, t7, and t8 shown in FIG. 3. Although details of the valley point detection unit 52 are omitted, for example, an auxiliary winding may be provided in the coil 35 and the voltage of the auxiliary winding may be detected to detect the valley point, or the current of the switching element 34 may be detected to detect the valley point. The valley point detection unit 52 may detect the valley point using other well-known methods.

[0050] The valley point counting section 53 counts the number of valley points of the resonance signal of the voltage generated across the switching element 34 based on the detection result of the valley point detection section 52 .

[0051] The timing control unit 54 acquires load information from an external device, and controls the timing of turning on the switching element 34 according to the count result of the valley points of the resonance signal by the valley point count unit 53 and the load information. The timing control unit 54 delays the timing of turning on the switching element 34 as the load information level indicates a lighter load. Specifically, the valley point count number of the resonance signal for turning on the switching element 34 according to the load information is determined as the on-timing valley point count number, and the switching element 34 is turned on at the timing when the count result of the valley point count unit 53 matches the on-timing valley point count number. In the first embodiment, the load information is load information of the LED element of the light-emitting unit 12. Specifically, the load information is a dimming signal indicating information on the brightness of the LED element. More specifically, the timing control unit 54 acquires at least one of output current information indicating the magnitude of the output current of the light-emitting unit 12 from the light-emitting unit 12 and a dimming signal indicating the illuminance. The switching control unit 51 turns on the switching element 34 according to the timing controlled by the timing control unit 54.

[0052] [Timing control method] A method for controlling the timing of turning on the switching element according to the first embodiment based on load information will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining the method for controlling the timing of turning on the switching element according to the first embodiment.

[0053] In FIG. 4, the horizontal axis indicates the level of the load information (dimming signal), and the vertical axis indicates the switching timing for turning on the switching element 34.

[0054] A control method when the level of the load information becomes lighter than the current level will be described. In Fig. 4, the load of the light-emitting unit 12 is indicated in the order of heavier load, from level L0 to level L1, level L2, level L3, and level L4. The brightness of the light-emitting unit 12 approaches full brightness as the load information approaches level L0, and approaches deep dimming as the load information approaches level L4.

[0055] In the first embodiment, when the level of the load information becomes lighter than the current level, the timing for turning on the switching element 34 is changed based on the load information levels L0, L1, L2, L3, and L4.

[0056] The timing control unit 54 sets the on-timing valley point count number to 1 when the load information is between level L0 and level L1. When the load information level is between level L1 and level L2, the timing control unit 54 sets the on-timing valley point count number to 2. When the load information level is between level L2 and level L3, the timing control unit 54 sets the on-timing valley point count number to 3. When the load information level is between level L3 and level L4, the timing control unit 54 sets the on-timing valley point count number to 4. When the load information level is level L4 or higher, the timing control unit 54 sets the on-timing valley point count number to 5. The timing control unit 54 turns on the switching element 34 at a timing when the determined on-timing valley point count number and the count result of the valley points of the resonance signal by the valley point count unit 53 match.

[0057] A control method when the load information level becomes heavier than the current level will be described. In Fig. 4, a level L1a with a heavier load than level L1, a level L2a with a heavier load than level L2, a level L3a with a heavier load than level L3, and a level L4a with a heavier load than level 4 are shown. That is, in the first embodiment, hysteresis is provided in the load information level for switching the switching timing for turning on the switching element 34 when the load information level becomes lighter and heavier than the current level.

[0058] In the first embodiment, when the load information level becomes heavier than the current level, the timing for turning on the switching element 34 is changed based on the load information levels L0, L1a, L2a, L3a, and L4a as reference levels.

[0059] The timing control unit 54 sets the on-timing valley point count number to 5 while the load information is at level L4a or higher. When the load information level is at level L3a or higher and at level L4a or lower, the timing control unit 54 sets the on-timing valley point count number to 4. When the load information level is at level L2a or higher and at level L3a or lower, the timing control unit 54 sets the on-timing valley point count number to 3. When the load information level is at level L1a or higher and at level L2a or lower, the timing control unit 54 sets the on-timing valley point count number to 2. When the load information level is at level L0 or higher and at level L1a or lower, the timing control unit 54 sets the on-timing valley point count number to 1. The timing control unit 54 turns on the switching element 34 at a timing when the determined on-timing valley point count number and the count result of the valley points of the resonance signal by the valley point count unit 53 match.

[0060] In the lighting device 1, when the load of the light-emitting unit 12 is heavy, the switching frequency is low, and when the load of the light-emitting unit 12 is light, the switching frequency is high. Therefore, if the switching element 34 is turned on too early when the load of the light-emitting unit 12 is light, switching loss increases. For this reason, in the first embodiment, the timing for turning on the switching element 34 is controlled according to the load of the light-emitting unit 12.

[0061] As described above, in the first embodiment, the heavier the load of the light-emitting unit 12 is, the earlier the timing at which the switching element 34 is turned on, and the lighter the load of the light-emitting unit 12 is, the later the timing at which the switching element 34 is turned on. This makes it possible for the first embodiment to reduce noise in the light-emitting unit 12. Furthermore, in the first embodiment, by controlling the timing at which the switching element 34 is turned on based on the load of the light-emitting unit 12, stable control can be achieved regardless of the load of the light-emitting unit 12.

[0062] In the first embodiment, the switching element 34 is turned on at the timing when the voltage of the resonance signal becomes minimum. In this way, in the first embodiment, switching loss can be reduced, and high efficiency can be achieved regardless of the load of the light-emitting unit 12.

[0063] In the first embodiment, the timing to turn on the switching element 34 is determined based on the load information of the light-emitting unit 12, so there is no need to use a complex configuration, and the cost of the entire device can be reduced.

[0064] [Second embodiment] Next, a timing control method according to a second embodiment of the present disclosure will be described. In the second embodiment, the timing to turn on the switching element 34 is controlled based on the time from when the switching element 34 is turned on until the switching element is turned off, a resonance signal is generated in the switching element 34, and the first valley of the resonance signal appears.

[0065] A configuration example of a control unit according to the second embodiment will be described with reference to Fig. 5. Fig. 5 is a block diagram showing a configuration example of a control unit according to the second embodiment.

[0066] As shown in FIG. 5, the control unit 21A differs from the control unit 21 shown in FIG.

[0067] FIG. 6 is a diagram for explaining a method for controlling the timing of turning on a switching element according to the second embodiment.

[0068] 6, the switching element 34 is turned on at timing t1, the switching element 34 is turned off at timing t2, and the time until the first valley point of the resonance signal appears at timing t4 is defined as time T. The timing control unit 54 changes the timing for turning on the switching element 34 depending on whether the measurement result of the time T by the time measurement unit 55 is less than a first time T1 or is equal to or greater than a second time T2 that is longer than the first time T1.

[0069] When the measurement result by the time measurement unit 55 is less than the first time T1, the timing control unit 54 determines the valley point count number of the resonance signal that turns on the switching element 34 as the on-timing valley point count number as the first count number, and turns on the switching element 34 at the timing when the count result of the valley point count unit 53 matches the on-timing valley point count number. When the measurement result by the time measurement unit 55 is equal to or greater than the second time T2 that is longer than the first time T1, the timing control unit 54 determines the valley point count number of the resonance signal that turns on the switching element 34 as the on-timing valley point count number as the second count number, and turns on the switching element 34 at the timing when the count result of the valley point count unit 53 matches the on-timing valley point count number. The first time T1 is, for example, 7.5 μsec, but is not limited to this. The second time T2 is, for example, 10 μsec, but is not limited to this. The first count number is a number greater than the second count number.

[0070] Specifically, for example, when the measurement result of the time measurement unit 55 is less than the first time T1, the timing control unit 54 sets the on-timing valley point count number to 3. For example, when the measurement result of the time measurement unit 55 is equal to or greater than the second time T2, the timing control unit 54 sets the on-timing valley point count number to 2. The timing control unit 54 turns on the switching element 34 at the timing when the determined on-timing valley point count number and the count result of the valley points of the resonance signal by the valley point count unit 53 match.

[0071] As described above, in the second embodiment, if the time from when the switching element 34 is turned on until the first valley of the resonance signal generated in the switching element 34 is reached is shorter than a predetermined first time, the timing to turn on the switching element 34 is delayed, and if the time is equal to or longer than a second time longer than the first time, the timing to turn on the switching element 34 is advanced. This makes it possible to reduce noise in the light-emitting unit 12 in the second embodiment.

[0072] [Third embodiment] Next, a third embodiment of the present disclosure will be described. In the third embodiment, the timing for turning on the switching element 34 is controlled by the resistance value of an external resistor connected to the control terminal of the control unit 21. In the third embodiment, the resistance value of the external resistor is determined at the time of designing the lighting device 1.

[0073] Fig. 7 is a diagram showing an example of the configuration of a control unit according to the third embodiment. As shown in Fig. 7, the control unit 21 includes a control terminal 61, a constant current source 62, a comparator 63, a threshold power supply 64, a comparator 65, and a threshold power supply 66.

[0074] The control terminal 61 is electrically connected to the output terminal of the constant current source 62 and the external resistor 71. The constant current source 62 is configured so that a voltage is input to the comparator 63 and the comparator 65 according to the external resistor 71 electrically connected to the control terminal 61. In other words, in this embodiment, a constant voltage pulled up according to the current value of the constant current output by the constant current source 62 and the resistance value of the external resistor 71 is input from the control terminal 61 to the comparator 63 and the comparator 65. The resistance value of the external resistor 71 can be arbitrarily changed according to the design.

[0075] The constant current source 62 is electrically connected between the power supply potential VD and the control terminal 61 .

[0076] A predetermined voltage according to the constant current source 62 and the external resistor 71 is input to the non-inverting input terminal of the comparator 63. That is, a predetermined voltage according to the design is input to the non-inverting input terminal of the comparator 63.

[0077] The inverting input terminal of the comparator 63 is electrically connected to a threshold power supply 64. A threshold voltage is input from the threshold power supply 64 to the inverting input terminal of the comparator 63. In the example shown in Fig. 7, the voltage value of the threshold voltage output from the threshold power supply 64 is, for example, 3 V, but is not limited to this.

[0078] Comparator 63 outputs a low-level signal when the voltage value of the voltage input to the non-inverting input terminal is less than 3 V. Comparator 63 outputs a high-level signal when the voltage value of the voltage input to the non-inverting input terminal is 3 V or more.

[0079] A predetermined voltage according to the constant current source 62 and the external resistor 71 is input to the non-inverting input terminal of the comparator 65. That is, a predetermined voltage according to the design is input to the non-inverting input terminal of the comparator 65.

[0080] A threshold power supply 66 is electrically connected to the inverting input terminal of the comparator 65. A threshold voltage is input from the threshold power supply 66 to the inverting input terminal of the comparator 65. In the example shown in Fig. 7, the voltage value of the threshold voltage output from the threshold power supply 66 is, for example, 1.5 V, but is not limited to this.

[0081] Comparator 65 outputs a low-level signal when the voltage value of the voltage input to the non-inverting input terminal is less than 1.5 V. Comparator 65 outputs a high-level signal when the voltage value of the voltage input to the non-inverting input terminal is 1.5 V or more.

[0082] That is, if the voltage value of the voltage input to each of the non-inverting input terminals of the comparators 63 and 65 is less than 1.5 V, the comparators 63 and 65 each output a low-level signal. If the voltage value of the voltage input to each of the non-inverting input terminals of the comparators 63 and 65 is 1.5 V or more and less than 3.0 V, the comparator 63 outputs a low-level signal and the comparator 65 outputs a high-level signal. If the voltage value of the voltage input to each of the non-inverting input terminals of the comparators 63 and 65 is 3 V or more, the comparators 63 and 65 each output a high-level signal.

[0083] In this embodiment, the timing to turn on the switching element 34 is controlled based on three patterns of the voltage value input to the non-inverting input terminals of the comparators 63 and 65 being less than 1.5 V, 1.5 V to 3 V, or 3 V or more. That is, in this embodiment, the timing to turn on the switching element 34 is controlled according to the voltage value of the control terminal 61.

[0084] A method of controlling the timing of turning on the switching element 34 based on the voltage of the control terminal 61 will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining a method of controlling the timing of turning on the switching element according to the third embodiment.

[0085] In Fig. 8, the horizontal axis represents time and the vertical axis represents voltage. If the voltage value of the control terminal 61 is less than 1.5V, it is determined that the switching element 34 is turned on at timing t3, which is the timing of the first valley point. If the voltage value of the control terminal 61 is 1.5V or more and less than 3V, it is determined that the switching element 34 is turned on at timing t4, which is the timing of the second valley point. If the voltage value of the control terminal 61 is 3V or more, it is determined that the switching element 34 is turned on at timing t5, which is the timing of the third valley point.

[0086] As described above, in the third embodiment, the timing at which the switching element 34 is turned on is made earlier as the voltage value of the control terminal 61 is smaller. This makes it possible to reduce noise in the light-emitting unit 12 in the third embodiment.

[0087] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described. In the fourth embodiment, the timing for turning on the switching element 34 is controlled by combining the first to third embodiments.

[0088] A method for controlling the timing of turning on the switching element according to the fourth embodiment will be described with reference to Fig. 9 and Fig. 10. Fig. 9 is a diagram for explaining a method for controlling the timing of turning on the switching element according to the fourth embodiment. Fig. 10 is a table for explaining a method for controlling the switching element according to the fourth embodiment.

[0089] 9, the horizontal axis indicates the level of the load information (dimming signal), and the vertical axis indicates the switching timing for turning on the switching element 34. In FIG 9, the switching timing is indicated by the Nth (N is any integer) valley point, the N+1th valley point, the N+2th valley point, and the N+3th valley point of the resonance signal.

[0090] In FIG. 9, the load information is divided into three regions according to the level. When controlling when the load information level becomes lighter than the current level, region A, region B, and region C are set according to the level of the load information. The load is heavier in the order of region A, region B, and region C. Region A is a region where the load weight is 67% or more when the load weight when the light-emitting unit 12 is in full dimming is 100%. Region B is a region where the load weight is 33% or more and 67% or less when the load weight when the light-emitting unit 12 is in full dimming is 100%. Region C is a region where the load weight is less than 33% when the load weight when the light-emitting unit 12 is in full dimming is 100%.

[0091] In addition, when controlling when the level of the load information becomes heavier than the current level, an Aa region with a heavier load than the A region, a Ba region with a heavier load than the B region, and a Ca region with a heavier load than the C region are set.

[0092] Fig. 10 is a table showing the timing to turn on the switching element 34 when the level of the load information becomes lighter than the current level. As shown in Fig. 10, in the fourth embodiment, the timing to turn on the switching element 34 is set according to a combination of the voltage of the control terminal 61, the switching period, and the load level.

[0093] When the voltage of the control terminal 61 is less than 1.5V, the switching period is 7.5μsec or less, and the load level is in region A, the timing control unit 54 determines to turn on the switching element 34 at the second valley point of the resonant signal. When the voltage of the control terminal 61 is less than 1.5V, the switching period is 7.5μsec or less, and the load level has changed from region A to region B, the timing control unit 54 determines to turn on the switching element 34 at the third valley point of the resonant signal. When the voltage of the control terminal 61 is less than 1.5V, the switching period is 7.5μsec or less, and the load level has changed from region B to region C, the timing control unit 54 determines to turn on the switching element 34 at the fourth valley point of the resonant signal.

[0094] When the voltage of the control terminal 61 is less than 1.5V, the switching period is 10μsec or more, and the load level is in region A, the timing control unit 54 determines to turn on the switching element 34 at the first valley point of the resonant signal. When the voltage of the control terminal 61 is less than 1.5V, the switching period is 10μsec or more, and the load level has changed from region A to region B, the timing control unit 54 determines to turn on the switching element 34 at the second valley point of the resonant signal. When the voltage of the control terminal 61 is less than 1.5V, the switching period is 10μsec or more, and the load level has changed from region B to region C, the timing control unit 54 determines to turn on the switching element 34 at the third valley point of the resonant signal.

[0095] When the voltage of the control terminal 61 is 1.5V or more and less than 3V, the switching period is 7.5μsec or less, and the load level is in region A, the timing control unit 54 determines to turn on the switching element 34 at the third valley point of the resonant signal. When the voltage of the control terminal 61 is 1.5V or more and less than 3V, the switching period is 7.5μsec or less, and the load level has changed from region A to region B, the timing control unit 54 determines to turn on the switching element 34 at the fourth valley point of the resonant signal. When the voltage of the control terminal 61 is 1.5V or more and less than 3V, the switching period is 7.5μsec or less, and the load level has changed from region B to region C, the timing control unit 54 determines to turn on the switching element 34 at the fifth valley point of the resonant signal.

[0096] When the voltage of the control terminal 61 is 1.5V or more and less than 3V, the switching period is 10μsec or more, and the load level is in region A, the timing control unit 54 determines to turn on the switching element 34 at the second valley point of the resonant signal. When the voltage of the control terminal 61 is 1.5V or more and less than 3V, the switching period is 10μsec or more, and the load level has changed from region A to region B, the timing control unit 54 determines to turn on the switching element 34 at the third valley point of the resonant signal. When the voltage of the control terminal 61 is 1.5V or more and less than 3V, the switching period is 10μsec or more, and the load level has changed from region B to region C, the timing control unit 54 determines to turn on the switching element 34 at the fourth valley point of the resonant signal.

[0097] When the voltage of the control terminal 61 is 3V or more, the switching period is 7.5μsec or less, and the load level is in region A, the timing control unit 54 determines to turn on the switching element 34 at the fourth valley point of the resonant signal. When the voltage of the control terminal 61 is 3V or more, the switching period is 7.5μsec or less, and the load level has changed from region A to region B, the timing control unit 54 determines to turn on the switching element 34 at the fifth valley point of the resonant signal. When the voltage of the control terminal 61 is 3V or more, the switching period is 7.5μsec or less, and the load level has changed from region B to region C, the timing control unit 54 determines to turn on the switching element 34 at the sixth valley point of the resonant signal.

[0098] When the voltage of the control terminal 61 is 3V or more, the switching period is 10μsec or more, and the load level is in region A, the timing control unit 54 determines to turn on the switching element 34 at the third valley point of the resonant signal. When the voltage of the control terminal 61 is 3V or more, the switching period is 10μsec or more, and the load level has changed from region A to region B, the timing control unit 54 determines to turn on the switching element 34 at the fourth valley point of the resonant signal. When the voltage of the control terminal 61 is 3V or more, the switching period is 10μsec or more, and the load level has changed from region B to region C, the timing control unit 54 determines to turn on the switching element 34 at the fifth valley point of the resonant signal.

[0099] As described above, in the fourth embodiment, the timing for controlling the switching element 34 is controlled according to a combination of the voltage of the control terminal 61, the switching period, and the load level. This makes it possible to reduce noise in the light-emitting unit 12 in the fourth embodiment.

[0100] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the contents of these embodiments. The above-mentioned components include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-mentioned components can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the above-mentioned embodiments. [Explanation of symbols]

[0101] 1 Lighting equipment 2 AC power supply 10. Switching power supply 11 PFC circuit section 12 Light emitting unit 20 Buck Converter 31 Input terminal 32,39 Ground terminal 33,37,42 Capacitor 34,44 Switching elements 35,43 Coil 36,45 Rectifier 38 Output terminal 41 Rectifier circuit 21, 21A Control section 51 Switching control section 52 Valley point detection unit 53 Valley Point Counting Section 54 Timing control section 55 Time measurement section

Claims

1. a buck converter including an input terminal, a switching element having a first terminal electrically connected to the input terminal, a coil having one end electrically connected to a second terminal of the switching element, an output terminal electrically connected to the other end of the coil, a rectifying element having a cathode electrically connected between the switching element and the coil and an anode electrically connected to a reference potential, and a capacitor having one end electrically connected to the output terminal and the other end electrically connected to the reference potential; A control unit that controls a switching operation of the switching element, The control unit is a valley point detection unit that stores magnetic energy by passing a current through the coil when the switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and detects a valley point of a resonance signal of a voltage generated across the switching element after all the magnetic energy in the coil has been released; a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit; a timing control unit that acquires a load information level from an external device and controls a timing for turning on the switching element in accordance with a count result of the valley points of the resonance signal by the valley point count unit and the load information level; a time measurement unit that measures a time from when the switching element is turned on until when the valley point detection unit detects a first valley point of the resonance signal; Equipped with the timing control section delays the timing of turning on the switching element as the load information level indicates a lighter load, and turns on the switching element at a timing when the count number of the valley point counting section is a first count number when the measurement result by the time measurement section is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting section is a second count number less than the first count number when the measurement result by the time measurement section exceeds a second time longer than the first time. Switching power supply.

2. the timing control unit turns on the switching element at a timing at which the first count number and the second count number are increased as the load information level indicates a lighter load.

2. The switching power supply device according to claim 1.

3. The control unit is A control terminal is provided which is pulled up to a predetermined voltage, The timing control unit is controlling a timing for turning on the switching element in response to a measured value of the voltage of the control terminal; 3. The switching power supply device according to claim 1 or 2.

4. The load information level is at least one of an output current of the lighting device and a dimming signal indicating illuminance.

4. The switching power supply device according to claim 1.

5. an input terminal; a switching element having a first terminal electrically connected to the input terminal; and a coil having one end electrically connected to a second terminal of the switching element; a buck converter including an output terminal electrically connected to the other end of the coil, a rectifying element having a cathode electrically connected between the switching element and the coil and an anode electrically connected to a reference potential, and a capacitor having one end electrically connected to the output terminal and the other end electrically connected to the reference potential; A control unit that controls a switching operation of the switching element, The control unit is a valley point detection unit that stores magnetic energy by passing a current through the coil when the switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and detects a valley point of a resonance signal of a voltage generated across the switching element after all the magnetic energy in the coil has been released; a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit; a time measurement unit that measures a time from when the switching element is turned on until when the valley point detection unit detects a first valley point of the resonance signal; a timing control unit that controls a timing for turning on the switching element in accordance with a count result of the valley points of the resonance signal by the valley point count unit and a time measurement result by the time measurement unit, the timing control unit turns on the switching element at a timing when the count number of the valley point counting unit is a first count number when the measurement result by the time measurement unit is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting unit is a second count number less than the first count number when the measurement result by the time measurement unit is more than a second time longer than the first time. Switching power supply.

6. an input terminal; a switching element having a first terminal electrically connected to the input terminal; and a coil having one end electrically connected to a second terminal of the switching element; a buck converter including an output terminal electrically connected to the other end of the coil, a rectifying element having a cathode electrically connected between the switching element and the coil and an anode electrically connected to a reference potential, and a capacitor having one end electrically connected to the output terminal and the other end electrically connected to the reference potential; A control unit that controls a switching operation of the switching element, The control unit is a valley point detection unit that stores magnetic energy by passing a current through the coil when the switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and detects a valley point of a resonance signal of a voltage generated across the switching element after all the magnetic energy in the coil has been released; a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit; A control terminal that is pulled up to a predetermined voltage; a timing control unit that controls a timing for turning on the switching element in response to a measured value of the voltage of the control terminal. Switching power supply.

7. a valley point detection unit that stores magnetic energy by passing a current through a coil when a switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and detects a valley point of a resonance signal of a voltage generated across the switching element after all the magnetic energy in the coil has been released; a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit; a timing control unit that acquires a load information level from an external device and controls a timing for turning on the switching element in accordance with a count result of the valley points of the resonance signal by the valley point count unit and the load information level; a time measurement unit that measures a time from when the switching element is turned on until when the valley point detection unit detects a first valley point of the resonance signal, the timing control section delays the timing of turning on the switching element as the load information level indicates a lighter load, and turns on the switching element at a timing when the count number of the valley point counting section is a first count number when the measurement result by the time measurement section is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting section is a second count number less than the first count number when the measurement result by the time measurement section exceeds a second time longer than the first time. Control device.

8. a valley point detection unit that stores magnetic energy by passing a current through a coil when a switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and detects a valley point of a resonance signal of a voltage generated across the switching element after all the magnetic energy in the coil has been released; a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit; a time measurement unit that measures a time from when the switching element is turned on until when the valley point detection unit detects a first valley point of the resonance signal; a timing control unit that controls a timing for turning on the switching element in accordance with a count result of the valley points of the resonance signal by the valley point count unit and a time measurement result by the time measurement unit, the timing control unit turns on the switching element at a timing when the count number of the valley point counting unit is a first count number when the measurement result by the time measurement unit is less than a first time, and turns on the switching element at a timing when the count number of the valley point counting unit is a second count number less than the first count number when the measurement result by the time measurement unit is more than a second time longer than the first time. Control device.

9. a valley point detection unit that stores magnetic energy by passing a current through a coil when a switching element is on, and releases the magnetic energy stored in the coil when the switching element is off, and detects a valley point of a resonance signal of a voltage generated across the switching element after all the magnetic energy in the coil has been released; a valley point counting unit that counts the number of the valley points based on a detection result of the valley point detection unit; and a timing control unit that controls a timing for turning on the switching element in response to a measured value of a voltage of a control terminal that is pulled up to a predetermined voltage. Control device.

Images