JP6694078B2 - Lighting device and lighting equipment - Google Patents

Description

  The present invention relates to a lighting device and a lighting fixture that light a light source.

  A luminaire using an LED (Light Emitting Diode) as a light source is regulated with respect to harmonics of an input current. In Japan, a limit value is determined for harmonics of an input current by Japanese Industrial Standards. .. Therefore, the lighting device has a PFC (Power Factor Correction) circuit that is a power factor correction circuit for suppressing harmonics of the input current and improving the power factor.

  Patent Document 1 discloses a method of suppressing an increase in switching frequency and suppressing a decrease in on-time during light load by switching the operation mode of the PFC circuit to current discontinuous mode control during light load. There is.

Japanese Patent No. 5152501

  The method disclosed in Patent Document 1 has a high harmonic suppression effect because the PFC circuit operates by the current critical mode control at the time of high output. However, the current critical mode control has a problem that the switching loss is large because the switching frequency is higher than that in the case of performing the current discontinuous mode control.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a lighting device capable of reducing switching loss while suppressing harmonics of an input current.

In order to solve the problems described above and achieve the object, a lighting device according to the present invention has a rectifier circuit that rectifies AC power, and a power output from the rectifier circuit that suppresses harmonics to improve the power factor. A DC conversion circuit that converts the DC power into DC power and supplies the DC power to the light source, and a control unit that controls the DC conversion circuit. And a coil through which the current output from the rectifier circuit flows, and the control unit turns off the switching element from the time when the current flowing through the coil becomes zero until the delay time set in the control unit elapses. by the delay to time turn on the switching element when the elapsed, the control unit, in a state where the light source is lit, the constant length of the delay time, the control unit, flows through the coil Comprises a period measuring unit for measuring a period in which the flow is zero, the control unit, depending on the measured period in the cycle measuring unit determines the length of the delay time.

  The lighting device according to the present invention has an effect of reducing switching loss while suppressing harmonics of the input current.

Configuration diagram of a lighting device and a lighting fixture according to the first embodiment The figure which shows the structure of the current control part shown in FIG. Timing chart showing the relationship between the current flowing in the light source, the current flowing in the coil, and the control signal of the MOSFET (Metal Oxide Semiconductor Field Effect Transistor) 1 is a timing chart showing the relationship between the current flowing through the coil forming the PFC circuit shown in FIG. 1, the drain voltage of the MOSFET, and the gate voltage of the MOSFET. The figure which shows the waveform at the time of dimming by the current critical mode control without providing a delay time. Diagram showing the waveform when dimming with a delay time The figure which shows the characteristics of the on-time and switching frequency of MOSFET which change according to the dimming ratio. The 1st figure which shows the on-time and switching frequency of MOSFET when delay time is changed according to dimming rate 2nd figure which shows the ON time and switching frequency of MOSFET when delay time is changed according to dimming rate FIG. 9 is a diagram showing a change over time in delay time, MOSFET on-time, and light source dimming rate when the delay time is extended from Tdelay1 to Tdelay2 with the dimming rate threshold 1 shown in FIG. 9 as a boundary. Flowchart for explaining the operation of the control unit when extending the delay time The figure which shows the time change of delay time, MOSFET on-time, and the dimming rate of a light source when shortening delay time from Tdelay2 to Tdelay1 on the threshold 1 of the dimming rate shown in FIG. Flowchart for explaining the operation of the control unit when reducing the delay time Configuration diagram of a lighting device and a lighting fixture according to a second embodiment Timing chart showing the relationship between the current flowing through the windings of the DC conversion circuit shown in FIG. 14, the drain voltage of the MOSFET, and the gate voltage of the MOSFET Configuration diagram of a lighting device and a lighting fixture according to a third embodiment Timing chart showing the relationship between the current flowing in the light source, the current flowing in the coil, and the control signal of the MOSFET The figure which shows the characteristics of the on-time and switching frequency of MOSFET which change according to the dimming ratio. The 1st figure which shows operation | movement of a current control part when the magnitude | size of the electric current output to a light source differs. The 2nd figure which shows operation | movement of a current control part when the magnitude | size of the electric current output to a light source differs. Configuration diagram of a lighting device and a lighting fixture according to a fourth embodiment In the fourth embodiment, a first timing chart showing the timing of measuring the zero current detection period Tzcd during the period from the state where the light source is turned off to the time when the light source starts to be turned on. In the fourth embodiment, a second timing chart showing the timing of measuring the zero current detection period Tzcd during the period from the state where the light source is turned off to the time when the light source starts to be turned on. The flowchart which shows operation | movement of the lighting device which concerns on Embodiment 4.

  Hereinafter, a lighting device and a lighting fixture according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a configuration diagram of a lighting device and a lighting fixture according to the first embodiment. The lighting fixture 200 is connected to the AC power supply 1 and converts the power supplied from the AC power supply 1 through the input filter 2 that smoothes the AC current output from the AC power supply 1 into a DC current that can be input to the light source 8. And a light source 8 that is turned on by the power supplied from the lighting device 100, and a dimmer 10 that outputs a dimming signal for turning on, turning off, or dimming the light source 8. .. The light source 8 is composed of an LED group in which a plurality of LEDs are directly connected. One end of the LED group is connected to the positive side DC bus P, and the other end of the LED group is connected to the negative side DC bus N.

  The lighting device 100 includes an input filter 2, a rectifier circuit 3 connected to the input filter 2, a capacitor 4 connected in parallel to the rectifier circuit 3, a DC conversion circuit 30, and a current detection for detecting a current flowing through the light source 8. It includes a unit 11 and a control unit 9 for controlling the PFC circuit 5 and the current control unit 7.

  The DC conversion circuit 30 has a function of suppressing the harmonics of the current input from the AC power supply 1 to improve the power factor and converting the power output from the rectifier circuit 3 into DC power and supplying the DC power to the light source 8. Have. The DC conversion circuit 30 includes a PFC circuit 5 for suppressing the harmonics of the current input from the AC power supply 1 to improve the power factor, a smoothing capacitor 6 for smoothing the output voltage of the PFC circuit 5, and a light source 8. And a current control unit 7 that controls the magnitude of the output current.

  The input filter 2 arranged between the AC power supply 1 and the rectifier circuit 3 has a coil 21 and a capacitor 22, and reduces high frequency noise superimposed on the current output from the AC power supply 1. The coil 21 is connected to the AC power supply 1 in series. One end of the coil 21 is connected to one end of the AC power supply 1, and the other end of the coil 21 is connected to the capacitor 22 and the rectifier circuit 3. The other end of the capacitor 22 is connected to the AC power supply 1 and the rectifier circuit 3.

  The rectifier circuit 3 is arranged between the input filter 2 and the PFC circuit 5, and converts the AC power supplied from the AC power supply 1 into DC power. The rectifier circuit 3 is composed of a diode bridge in which four diodes are combined. The configuration of the rectifier circuit 3 is not limited to this, and may be a combination of MOSFETs that are unidirectional conducting elements.

  The capacitor 4 is connected in parallel to the output of the rectifier circuit 3 and smoothes the output voltage of the rectifier circuit 3. One end of the capacitor 4 is connected to the positive side DC bus P, and the other end of the capacitor 4 is connected to the negative side DC bus N.

  The PFC circuit 5 is arranged between the rectifier circuit 3 and the current controller 7. The PFC circuit 5 has a MOSFET 51 that is a switching element, a coil 52, and a diode 53. The PFC circuit 5 boosts the output voltage of the rectifier circuit 3 and outputs the boosted voltage to the smoothing capacitor 6 when the MOSFET 51 is turned on / off by the control unit 9. Further, the PFC circuit 5 has a function of suppressing harmonics of the input current and improving the power factor by the control described later. In the first embodiment, an example in which the PFC circuit 5 is composed of a boost chopper circuit will be described. The PFC circuit 5 may be configured by a circuit such as a step-up / step-down chopper circuit, a flyback circuit, a flyforward circuit, a SEPIC (Single Ended Primary Inductor Converter), a Zeta converter, or a Cuk converter other than the boost chopper circuit.

  The coil 52 is arranged between the capacitor 4 and the MOSFET 51 on the positive-side DC bus P. A primary winding 52a and a secondary winding 52b are formed on the coil 52 by winding an insulating wire around a core (not shown). One end of the primary winding 52a is connected to one end of the capacitor 4. The other end of the primary winding 52a is connected to the anode of the diode 53. One end of the secondary winding 52b is connected to the control unit 9, and the other end of the secondary winding 52b is connected to the negative side DC bus N. Voltages having different polarities are applied to the primary winding 52a as the MOSFET 51 is turned on and off. The voltage generated in the secondary winding 52b is equal to the voltage according to the applied voltage of the primary winding 52a and the turn ratio n.

  The drain of the MOSFET 51 is connected to the primary winding 52a and the anode of the diode 53 at the positive-side DC bus P. The source of the MOSFET 51 is connected to the other end of the capacitor 4, the other end of the secondary winding 52b, and the other end of the smoothing capacitor 6 at the negative-side DC bus N. The gate of the MOSFET 51 is connected to the control unit 9. A control signal output from the control unit 9 is input to the gate of the MOSFET 51. On-off control of the MOSFET 51 is performed by inputting the control signal.

  The diode 53 is arranged between the MOSFET 51 and the smoothing capacitor 6 on the positive-side DC bus P. The anode of the diode 53 is connected to the coil 52 and the MOSFET 51, and the cathode of the diode 53 is connected to the smoothing capacitor 6.

  The smoothing capacitor 6 is arranged between the PFC circuit 5 and the current controller 7. One end of the smoothing capacitor 6 is connected to the positive electrode side DC bus P, and the other end of the smoothing capacitor 6 is connected to the negative electrode side DC bus N.

  The current detector 11 detects a current flowing through the light source 8 and outputs current information corresponding to the detected current value to the controller 9. The current detection unit 11 may be configured to detect a current using a shunt resistor or a Hall sensor.

  The control unit 9 includes a target value output unit 91, a zero current detection unit 92, a switching control unit 93, a current input unit 94, and a voltage detection unit 95.

  The dimmer 10 is connected to the target value output unit 91, and the target value output unit 91 determines the output current target value corresponding to the type of the dimming signal output from the dimmer 10 and determines the determined output current. The target value is output to the switching control unit 93. The output current target value is a signal that specifies the current target value that the lighting device 100 outputs to the light source 8.

  The voltage detection unit 95 detects the voltage of the smoothing capacitor 6 and outputs voltage information corresponding to the detected voltage value to the switching control unit 93. A voltage dividing circuit can be exemplified as the voltage detecting unit 95. In the voltage dividing circuit, one end of a series resistor in which two resistors are connected in series is connected to the positive electrode side DC bus P, and the other end of the series resistor is connected to the negative electrode DC bus N, This is a circuit that divides the voltage applied to the smoothing capacitor 6.

  The switching control unit 93 outputs a control signal for controlling the current control unit 7 based on the output current target value output from the target value output unit 91 and the current information input to the current input unit 94. Further, the switching control unit 93 stores the output voltage target value of the PFC circuit 5 in advance, and based on at least the voltage information output from the voltage detection unit 95 and the stored output voltage target value, the PFC circuit 5. Output a control signal for controlling.

  The current controller 7 converts the DC voltage output from the PFC circuit 5 into a DC current that can be input to the light source 8 based on the control signal output from the switching controller 93.

  FIG. 2 is a diagram showing the configuration of the current control unit shown in FIG. The current control unit 7 shown in FIG. 2 is configured by a step-down chopper circuit, but in addition to the step-down chopper circuit, a circuit such as a step-up / step-down chopper circuit, flyback circuit, flyforward circuit, SEPIC, Zeta converter, or Cuk converter. It may be composed of.

  The current controller 7 includes a MOSFET 71, a coil 72, a diode 73 and a capacitor 74. The MOSFET 71 is arranged on the DC bus P on the positive electrode side. The drain of the MOSFET 71 is connected to one end of the smoothing capacitor 6 shown in FIG. 1 and the cathode of the diode 53. The source of the MOSFET 71 is connected to the cathode of the diode 73 and one end of the coil 72. The gate of the MOSFET 71 is connected to the switching control unit 93. The control signal output from the switching control unit 93 is input to the gate of the MOSFET 71. The control signal is a signal for on / off controlling the MOSFET 71.

  One end of the coil 72 is connected to the source of the MOSFET 71 and the cathode of the diode 73. The other end of the coil 72 is connected to one end of the capacitor 74 and one end of the light source 8 shown in FIG. The cathode of the diode 73 is connected to the source of the MOSFET 71 and one end of the coil 72. The anode of the diode 73 is connected to the other end of the smoothing capacitor 6 shown in FIG. 1, the other end of the capacitor 74, and the other end of the light source 8 shown in FIG.

  FIG. 3 is a timing chart showing the relationship between the current flowing through the light source, the current flowing through the coil, and the control signal of the MOSFET. In FIG. 3, the current flowing through the light source 8, the current flowing through the coil 72, and the control signal of the MOSFET 71 are shown in order from the top. The horizontal axis represents time.

  The switching cycle Tsw is equal to the time from when the control signal of the MOSFET 71 changes from OFF to ON until when the control signal of the MOSFET 71 changes from OFF to ON again. The switching cycle Tsw is preset in the switching control unit 93. The on-time Ton is equal to the time from when the control signal of the MOSFET 71 changes from off to on until it changes from on to off.

  When the control signal of the MOSFET 71 changes from the off state to the on state, the MOSFET 71 is turned on, so that a current path through which a current flows is formed in the smoothing capacitor 6, the MOSFET 71, the coil 72, and the capacitor 74, and as shown in FIG. The current flowing through 72 increases.

  When the control signal of the MOSFET 71 changes from the on state to the off state, the MOSFET 71 is turned off, so that a current path through which the current flows through the coil 72, the capacitor 74 and the diode 73 is formed, and the current flowing through the coil 72 shown in FIG. Decrease to zero. When the switching cycle Tsw elapses, the control signal of the MOSFET 71 changes from off to on. As a result, the MOSFET 71 is turned on again.

  At this time, the current flowing through the coil 72 has a triangular waveform, but the current output to the light source 8 is smoothed by the capacitor 74, and the average value of the current flowing through the coil 72 is output from the current controller 7.

  When controlling the current flowing through the light source 8 for dimming the light source 8, the switching control unit 93 keeps the switching cycle Tsw for turning on the MOSFET 71 constant, and changes the on-time Ton according to the target value of the output current. The control method for obtaining a specific output by adjusting the on-time Ton in this way is called duty control because the ratio of the on-time Ton to the switching cycle Tsw is called duty.

  The MOSFETs 51 and 71, which are switching elements, are made of a silicon material. However, the materials of the MOSFETs 51 and 71 are not limited to silicon-based materials, and the MOSFETs 51 and 71 may be composed of a wide band gap semiconductor such as silicon carbide, gallium nitride-based material, or diamond.

  By using a wide band gap semiconductor for the switching element, the conduction loss of the switching element can be reduced. Further, the switching element composed of a wide band gap semiconductor has high heat resistance. Further, the switching element composed of the wide band gap semiconductor has a faster switching speed and the loss generated at the time of switching is smaller than that of the switching element composed of the silicon material. Therefore, by increasing the switching frequency, that is, the driving frequency, even if the switching element is switched at high speed, it is possible to downsize the heat dissipation component for dissipating the heat generated in the switching element. Therefore, the heat dissipation components provided in the PFC circuit 5 and the current controller 7 can be downsized or the heat dissipation components can be omitted. As a result, downsizing and cost reduction of the lighting device 100 can be realized.

  Next, the operation of the PFC circuit 5 will be described in detail.

  FIG. 4 is a timing chart showing the relationship between the current flowing through the coil forming the PFC circuit shown in FIG. 1, the drain voltage of the MOSFET, and the gate voltage of the MOSFET. In FIG. 4, the current of the AC power supply 1 input to the lighting device 100, the current flowing through the coil 52, the drain voltage of the MOSFET 51, and the gate voltage of the MOSFET 51 are shown in order from the top. The horizontal axis represents time. In FIG. 4, the current of the AC power supply 1 input to the lighting device 100 is shown as “input current”.

  In FIG. 4, for convenience of explanation, the cycle in which the gate voltage of the MOSFET 51 is turned on and off is described longer than it actually is. The period in which the gate voltage of the MOSFET 51 is turned on / off is equal to the time from when the gate voltage of the MOSFET 51 changes from off to on until the gate voltage of the MOSFET 51 changes from off to on again.

  When the MOSFET 51 is turned on, a closed circuit is formed by the AC power supply 1, the rectifier circuit 3, the coil 52 and the MOSFET 51, and the AC power supply 1 is short-circuited via the coil 52. Therefore, the power supply current flows through the closed circuit, the current flowing through the coil 52 increases, and energy is accumulated in the coil 52.

  When the ON time set in the switching control unit 93 elapses, the MOSFET 51 is turned off to form a closed circuit of the coil 52, the diode 53 and the smoothing capacitor 6. In this closed circuit, the energy stored in the coil 52 is released and the smoothing capacitor 6 is charged.

  The MOSFET 51 is kept in the off state until the delay time Tdelay elapses from the time when the current flowing through the coil 52 becomes zero, and the MOSFET 51 is turned on again when the delay time Tdelay elapses. That is, the control signal of the MOSFET 51 remains off from the time when the current flowing through the coil 52 becomes zero to the time when the delay time Tdelay elapses, and the control signal of the MOSFET 51 turns on when the delay time Tdelay elapses. Change.

  Due to a series of on / off operations of the MOSFET 51, the current flowing through the coil 52 has a triangular waveform, and the apex thereof has a sinusoidal envelope as shown by the dotted line.

  At this time, the current input from the AC power supply 1 is smoothed by the input filter 2 and the average value of the coil current flowing in the coil 21 is input, so that a sinusoidal current waveform is obtained.

  The control unit 9 detects the voltage applied to the smoothing capacitor 6 and is feedback-controlled so that the detected voltage follows the target value, whereby the on-time of the MOSFET 51 is controlled.

  When the on-time of the MOSFET 51 is feedback-controlled, if the on-time greatly changes, the envelope curve of the apex of the current flowing through the coil 52 does not have a sine wave, and the input current of the AC power supply 1 can have a sine wave shape. Can not. Therefore, in the control unit 9, the response time of the feedback control is set so that the loop gain of the feedback control becomes 1 time (0 dB) or less when it is ½ cycle or more of one cycle of the AC power supply 1. In other words, the response time of the feedback control is set to be 1 time (0 dB) or less at a frequency that is 2 times or less the frequency of the AC power supply 1.

  More specifically, when the power supply frequency is 50 Hz, the loop gain of the feedback control is set to 1 time (0 dB) or less by setting the frequency of the half cycle (half wave) of the power supply frequency to 100 Hz or less, that is, the cycle of 10 msec or more. The feedback control is set so as not to respond in a cycle shorter than 1/2 of the power supply cycle. As a result, the variation of the on-time of the MOSFET 51 is suppressed and the envelope of the peak of the current flowing through the coil 52 has a sinusoidal waveform within 1/2 cycle of the power supply cycle.

  Further, in the feedback control, the same effect can be obtained by setting the update period of the on-time to a period corresponding to half the period of the AC power supply 1 or a period longer than the period corresponding to half of the AC power supply 1. Obtainable.

  In the technique disclosed in the above-mentioned Patent Document 1, the MOSFET 51 is switching-controlled by the current critical mode control without providing the delay time Tdelay, so that the average value of the current flowing through the coil 52 becomes a perfect sine wave and a high force is obtained. Rate improvement effect can be expected.

  On the other hand, the lighting device 100 according to the first embodiment provides the delay time Tdelay and controls the switching of the MOSFET 51 by the current discontinuous mode control, thereby lowering the switching frequency as compared with the case of the current critical mode control. Therefore, the switching loss generated in the MOSFET 51 can be reduced.

  At this time, if the delay time Tdelay is made too long, the current average value of the coil 52 is not a sine wave, the power factor improving effect is reduced, and harmonics are increased. Therefore, the delay time Tdelay needs to be set within a range in which the increase of harmonics is allowable. An example of the range in which the increase of harmonics is allowable is to be within the current harmonic limit value defined by Japanese Industrial Standards. As a specific method of providing the delay time Tdelay, the control unit 9 turns on the MOSFET 51 near the bottom of the voltage oscillation of the MOSFET 51 during the period when the drain voltage of the MOSFET 51 is freely oscillating, so that the drain voltage is steep. It is possible to suppress fluctuation and suppress noise due to switching. The voltage oscillation represents the oscillation of the drain voltage, and the bottom represents the valley portion of the oscillation of the drain voltage. In addition, the control unit 9 turns on the MOSFET 51 at least at the bottom of the voltage oscillation of the MOSFET 51 at least for the second time and thereafter, so that the delay time can be reliably provided.

  When dimming the light source 8, the switching control unit 93 controls to shorten the ON time of the MOSFET 51 in order to reduce the input current of the AC power supply 1.

  FIG. 5 is a diagram showing a waveform when dimming by current critical mode control without providing a delay time, and FIG. 6 is a diagram showing a waveform when dimming by providing a delay time. 5 and 6 are for explaining the outline of the switching operation of the PFC circuit 5 when the light source 8 is dimmed. Similar to FIG. 4, each of FIG. 5 and FIG. 6 shows the input current of the AC power supply 1, the current flowing through the coil 52, the drain voltage of the MOSFET 51, and the gate voltage of the MOSFET 51. The horizontal axis represents time.

  When the delay time Tdelay is provided as shown in FIG. 6, the switching frequency of the MOSFET 51 is lowered and the switching loss can be reduced, as compared with the case where the dimming is performed by the current critical mode control as shown in FIG.

  FIG. 7 is a diagram showing the characteristics of the MOSFET on-time and switching frequency that change according to the dimming ratio. In FIG. 7, the delay time Tdelay, the ON time of the MOSFET 51, the switching frequency of the control signal for controlling the MOSFET 51, and the dimming ratio of the light source 8 are shown in order from the top.

  The dotted line represents the delay time Tdelay, the ON time of the MOSFET 51, and the switching frequency when the dimming ratio is changed when the current critical mode control is performed. The solid line represents the delay time Tdelay, the ON time of the MOSFET 51, and the switching frequency when the dimming ratio is changed when the current discontinuous mode control in which the delay time is set is being performed.

  By providing the delay time Tdelay and performing the current discontinuous mode control, it is possible to suppress an increase in the switching frequency during dimming and reduce the switching loss as compared with the current critical mode control. Further, the on time of the MOSFET 51 can be lengthened, and the on / off control of the MOSFET 51 can be performed more reliably.

  Further, the delay time Tdelay is not a fixed length and can be changed according to the dimming rate. FIG. 8 is a first diagram showing the on-time and the switching frequency of the MOSFET when the delay time is changed according to the dimming rate.

  As shown in FIG. 8, a threshold value is provided for the dimming rate, and when the dimming rate exceeds the threshold value, the control unit 9 sets the delay time to a constant first delay time Tdelay1st and sets the dimming rate to the threshold value. In the following cases, the delay time is the second delay time Tdelay2nd. The second delay time Tdelay2nd is longer than the first delay time Tdelay1st and is longer as the dimming rate decreases.

  It is assumed that the threshold value, the first delay time Tdelay1st, and the second delay time Tdelay2nd shown in FIG. 8 are set in the control unit 9 in advance. The first delay time Tdelay1st is set when a dimming rate that exceeds the threshold is input, and the second delay time Tdelay2nd is set when a dimming rate that is less than or equal to the threshold is input.

  If the ON time of the MOSFET 51 becomes too short, the MOSFET 51 may not operate normally on / off. The length of on-time during which the MOSFET 51 cannot normally operate on / off is, for example, 0.2 sec or less. Therefore, the minimum on-time Ton_min is stored in the control unit 9, and when the light source 8 is dimmed, dimming control can be performed so that the on-time of the MOSFET 51 is not shorter than the minimum on-time Ton_min.

  FIG. 9 is a second diagram showing the on-time and the switching frequency of the MOSFET when the delay time is changed according to the dimming rate. As shown in FIG. 9, a plurality of threshold values 1, 2, and 3 are set for the dimming rate. The plurality of thresholds 1, 2, and 3 have higher values in the order of threshold 3, threshold 2, and threshold 1. Further, as shown in FIG. 9, a plurality of delay times Tdelay 1, 2, 3, 4 corresponding to a plurality of thresholds 1, 2, 3 are set. It is assumed that the plurality of thresholds 1, 2, 3 and the plurality of delay times Tdelay 1, 2, 3, 4 are set in the control unit 9.

  The delay time Tdelay4 is set when a dimming ratio equal to or less than the threshold value 3 is input. The delay time Tdelay3 is set when the dimming rate that exceeds the threshold value 3 and is equal to or less than the threshold value 2 is input. The delay time Tdelay2 is set when the dimming ratio that exceeds the threshold 2 and is equal to or less than the threshold 1 is input. The delay time Tdelay1 is set when a dimming ratio exceeding the threshold value 1 is input.

  The control unit 9 sets a plurality of threshold values for the dimming rate, and controls the switching element using a plurality of delay times having different lengths according to the range between the adjacent threshold values. Specifically, when the delay time Tdelay1 is provided and the light is turned on, when the current of the light source 8 is dimmed and the dimming rate reaches the threshold value 1, the on-time of the MOSFET 51 is minimum. When the time is shortened to Ton_min, the control unit 9 increases the delay time from Tdelay1 to Tdelay2. This can prevent the on-time of the MOSFET 51 from becoming shorter than the minimum on-time Ton_min.

  FIG. 10 is a diagram showing the time variation of the delay time, the on-time of the MOSFET, and the dimming ratio of the light source when the delay time is extended from Tdelay1 to Tdelay2 with the dimming ratio threshold 1 shown in FIG. 9 as a boundary. is there.

  When the delay time Tdelay is suddenly extended, the switching frequency of the MOSFET 51 suddenly changes, the output of the PFC circuit 5 fluctuates, and the voltage of the smoothing capacitor 6 fluctuates, so that the output current of the current control unit 7 connected in the subsequent stage is constant. It does not have a value, and the light source 8 cannot be stably turned on. Therefore, when the delay time Tdelay is extended, the change amount maximum value Tstep of the delay time Tdelay is provided, and the maintenance time Tk for maintaining the delay time Tdelay without changing is provided to delay the time change of the delay time Tdelay. be able to. By performing this control, it is possible to suppress a sudden change in the switching frequency of the MOSFET 51.

  At this time, the maintenance time Tk for maintaining the delay time Tdelay is set to be longer than the response time for feedback controlling the ON time of the MOSFET 51. As a result, the time when the on-time of the MOSFET 51 becomes a constant value is secured, and the output of the PFC circuit 5 can be stabilized.

  Next, the control when the delay time is extended from Tdelay1 to Tdelay2 will be described in more detail with reference to FIG. FIG. 11 is a flowchart for explaining the operation of the control unit when extending the delay time.

  When the light source 8 is turned on with the delay time Tdelay 1 provided, the control unit 9 performs dimming in the direction of decreasing the current of the light source 8 (S11), and when the dimming rate is larger than the threshold value 1 (S12, No). ), The delay time is not changed (S15). When the dimming ratio is less than or equal to the threshold value 1 (S12, Yes), the control unit 9 does not change the delay time unless the maintenance time Tk of the delay time has elapsed after the final change of the delay time (S13, No). (S15). When the delay time maintenance time Tk has elapsed after the final change of the delay time (S13, Yes), the control unit 9 does not change the delay time if the delay time is Tdelay2 or more (S14, No) (S14, No). S15). If the delay time is smaller than Tdelay2 (S14, Yes), the delay time is extended by Tstep (S16).

  On the contrary, when the delay time Tdelay2 is provided and the light source 8 is dimmed in the direction of increasing the current and the dimming rate reaches the threshold value 1, the control unit 9 changes the delay time from Tdelay2 to Tdelay1. Shorten to.

  FIG. 12 is a diagram showing the time variation of the delay time, the on-time of the MOSFET, and the dimming ratio of the light source when the delay time is shortened from Tdelay2 to Tdelay1 with the dimming ratio threshold 1 shown in FIG. is there. When the delay time is sharply shortened, the switching frequency of the MOSFET 51 suddenly changes, the output of the PFC circuit 5 fluctuates, and the voltage of the smoothing capacitor 6 fluctuates. Therefore, the light source 8 cannot be stably turned on. Therefore, when the delay time Tdelay is shortened, the change amount maximum value Tstep of the delay time Tdelay is provided, and the maintenance time Tk for maintaining the delay time Tdelay without changing is provided to delay the time change of the delay time Tdelay. can do. By performing this control, it is possible to suppress a sudden change in the switching frequency of the MOSFET 51.

  At this time, the sustain time Tk for maintaining the delay time Tdelay is set to be longer than the response time for feedback controlling the on time of the MOSFET 51. As a result, the time when the on-time of the MOSFET 51 becomes a constant value is secured, and the output of the PFC circuit 5 can be stabilized.

  Next, the control when the delay time is shortened from Tdelay2 to Tdelay1 will be described in more detail with reference to FIG. FIG. 13 is a flowchart for explaining the operation of the control unit when reducing the delay time.

  The control unit 9 performs dimming in the direction of increasing the current of the light source 8 from the state of lighting with the delay time Tdelay 2 provided (S21), and when the dimming rate is equal to or less than the threshold value 1 (S22, No), The delay time is not changed (S25). When the dimming rate is larger than the threshold value 1 (S22, Yes), if the delay time maintenance time Tk has not elapsed after the final change of the delay time (S23, No), the delay time is not changed (S25). When the delay time maintenance time Tk has elapsed after the final change of the delay time (S23, Yes), the control unit 9 does not change the delay time if the delay time is Tdelay1 or less (S24, No) (S24, No). S25). If the delay time is longer than Tdelay1 (S24, Yes), the delay time is shortened by Tstep (S26).

  Even when the dimming ratio of the light source 8 is changed and the dimming ratio becomes the threshold 2 and the threshold 3, the same control as that in the case of the threshold 1 is performed.

  In the first embodiment, the case where the light source 8 is composed of the LED has been described, but the light source 8 is not limited to the LED as long as it is dimmable, and may be an organic EL (Electro Luminescence).

Embodiment 2.
FIG. 14 is a configuration diagram of the lighting device and the lighting fixture according to the second embodiment. In the second embodiment, parts having the same configurations as those of the lighting device 100 and the lighting fixture 200 shown in the first embodiment in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

  The difference between the lighting fixture 200A according to the second embodiment and the lighting fixture 200 according to the first embodiment is that the lighting fixture 100A is used instead of the lighting fixture 100 in the lighting fixture 200A. Further, the difference between the lighting device 100A according to the second embodiment and the lighting device 100 according to the first embodiment is that in the lighting device 100A, instead of the PFC circuit 5, the smoothing capacitor 6, and the current control unit 7, a DC conversion circuit. 12 is used, and the control unit 9A is used instead of the control unit 9. The DC conversion circuit 12 is a circuit that also has the functions of the PFC circuit 5, the smoothing capacitor 6, and the current control unit 7.

  In the second embodiment, an example in which the DC conversion circuit 12 is composed of a flyback circuit will be described. In addition to the flyback circuit, the DC conversion circuit 12 may be configured by a flyforward circuit, a step-down chopper, a step-up chopper, a step-up / step-down chopper circuit, SEPIC, a Zeta converter, or a Cuk converter.

  The DC conversion circuit 12 includes a MOSFET 121, a transformer 122, a diode 123, a smoothing capacitor 124, a snubber capacitor 125, a snubber resistor 126, and a snubber diode 127.

  MOSFET 121 is arranged between negative electrode side DC bus N and capacitor 4 and the primary side of transformer 122. The source of the MOSFET 121 is connected to one end of the capacitor 4 and the rectifier circuit 3. The drain of the MOSFET 121 is connected to the anode of the snubber diode 127 and the transformer 122. The snubber capacitor 125, the snubber resistor 126, and the snubber diode 127 are arranged between the capacitor 4 and the primary side of the transformer 122.

  One end of the snubber resistor 126 is connected to the other end of the capacitor 4, the rectifier circuit 3, one end of the snubber capacitor 125, and the transformer 122 via the positive-side DC bus P. The other end of the snubber resistor 126 is connected to the other end of the snubber capacitor 125 and one end of the snubber diode 127. The other end of the snubber capacitor 125 is connected to the other end of the snubber resistor 126 and one end of the snubber diode 127. The diode 123 and the smoothing capacitor 124 are arranged between the secondary side of the transformer 122 and the light source 8. The anode of the diode 123 is connected to the transformer 122, and the cathode of the diode 123 is connected to one end of the smoothing capacitor 124 and one end of the light source 8. The other end of the smoothing capacitor 124 is connected to the transformer 122 and the other end of the light source 8.

  By winding an insulating wire around a core (not shown), a primary winding 122a, a secondary winding 122b, and a tertiary winding 122c are formed in the transformer 122.

  The DC conversion circuit 12 converts the output voltage of the rectifier circuit 3 and outputs a DC current to the light source 8 by controlling the MOSFET 121 to be turned on and off.

  The control unit 9A includes a target value output unit 91, a zero current detection unit 92, a switching control unit 93A, and a current input unit 94. The difference between the control unit 9 shown in FIG. 1 and the control unit 9A shown in FIG. 14 is that in the control unit 9A, the voltage detection unit 95 is omitted and the switching control unit 93A is used instead of the switching control unit 93. That is.

  The operation of the DC conversion circuit 12 will be described in detail.

  FIG. 15 is a timing chart showing the relationship between the current flowing through the windings of the DC conversion circuit shown in FIG. 14, the drain voltage of the MOSFET, and the gate voltage of the MOSFET. In FIG. 15, in order from the top, the current of the AC power supply 1 input to the lighting device 100A, the current flowing through the primary winding 122a, the current flowing through the tertiary winding 122c, the drain voltage of the MOSFET 121, and the MOSFET 121. And the gate voltage of The horizontal axis represents time. In FIG. 15, the current of the AC power supply 1 input to the lighting device 100A is shown as “input current”.

  In FIG. 15, for convenience of explanation, the cycle in which the gate voltage of the MOSFET 121 is turned on and off is described longer than it actually is. The period in which the gate voltage of the MOSFET 121 is turned on / off is equal to the time from when the gate voltage of the MOSFET 121 changes from off to on, until the gate voltage of the MOSFET 121 changes from off to on again.

  When the MOSFET 121 is turned on, a closed circuit is formed by the AC power supply 1, the rectifier circuit 3, the primary winding 122a, and the MOSFET 121, and the AC power supply 1 is short-circuited via the primary winding 122a. Therefore, the power supply current flows through the closed circuit, the current flowing through the primary winding 122a increases, and energy is accumulated in the primary winding 122a.

  When the ON time set in the switching control unit 93A elapses, the MOSFET 121 is turned off to form a closed circuit of the tertiary winding 122c, the diode 123, and the smoothing capacitor 124. In this closed circuit, the energy stored in the primary winding 122a is released and the smoothing capacitor 124 is charged.

  The MOSFET 121 is kept in the off state until the delay time Tdelay elapses from the time when the current flowing through the tertiary winding 122c becomes zero, and the MOSFET 121 is turned on again when the delay time Tdelay elapses.

  Due to a series of on / off operations of the MOSFET 121, the current flowing through the primary winding 122a has a triangular waveform, and its apex has a sinusoidal envelope as shown by a dotted line.

  At this time, the current input from the AC power supply 1 is smoothed by the input filter 2 and the average value of the coil current flowing in the coil 21 is input, so that a sinusoidal current waveform is obtained.

  The on-time of the MOSFET 121 is controlled by the control unit 9A detecting the current flowing through the light source 8 and performing feedback control so that the detected current follows the target value.

  When the on-time of the MOSFET 121 is feedback-controlled, if the on-time greatly changes, the envelope of the apex of the current flowing through the primary winding 122a does not become a sine wave, and the input current of the AC power supply 1 becomes a sine wave. Can not do it. Therefore, in the control unit 9A, the response time of the feedback control is set so that the loop gain of the feedback control is 1 time (0 dB) or less when it is ½ cycle or more of one cycle of the AC power supply 1. In other words, the response time of the feedback control is set to be 1 time (0 dB) or less at a frequency that is 2 times or less the frequency of the AC power supply 1.

  More specifically, when the power supply frequency is 50 Hz, the loop gain of the constant current feedback control should be 1 time (0 dB) or less at a frequency of 100 Hz or less of a half cycle (half wave) of the power supply frequency, that is, a cycle of 10 msec or more. Thus, the constant current feedback control is set so as not to respond in a cycle shorter than 1/2 of the power supply cycle. As a result, the variation of the on-time of the MOSFET 121 is suppressed and the envelope of the peak of the current flowing through the primary winding 122a has a sinusoidal waveform within 1/2 cycle of the power supply cycle.

  Further, in the feedback control, the same effect can be obtained by setting the update period of the on-time to a period corresponding to half the period of the AC power supply 1 or a period longer than the period corresponding to half of the AC power supply 1. Obtainable.

  The lighting device 100A and the lighting fixture 200A according to the second embodiment are provided with the delay time Tdelay similarly to the first embodiment, and perform the switching control of the MOSFET 121 by the current discontinuous mode control, thereby performing the current critical mode control. In comparison, since the switching frequency can be lowered, the switching loss generated in MOSFET 121 can be reduced.

  In the first and second embodiments, the example in which the length of the delay time is changed according to the dimming rate has been described, but the length of the delay time is the output that the DC conversion circuit 30 outputs to the LED instead of the dimming rate. The determination may be made based on the current target value. Further, in this case, the magnitude of the output of the DC conversion circuit may be determined based on the dimming rate of the LED, may be determined based on the output current target value of the LED, or may be based on the dimming rate of the organic EL. It may be determined. Further, the magnitude of the output of the DC conversion circuit may be determined from the output current target value of the LED. Further, the control unit according to the first and second embodiments may be configured to change the length of the delay time according to the output current target value instead of the dimming rate.

Embodiment 3.
FIG. 16 is a configuration diagram of the lighting device and the lighting fixture according to the third embodiment. In addition, in the third embodiment, parts having the same configurations as those of the lighting device 100 and the lighting fixture 200 according to the first embodiment of FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

  The difference between the lighting fixture 200B according to Embodiment 3 and the lighting fixture 200 according to Embodiment 1 is that the lighting fixture 100B is used in place of the lighting fixture 100 in the lighting fixture 200B. Further, the difference between the lighting device 100B according to the third embodiment and the lighting device 100 according to the first embodiment is that in the lighting device 100B, the coil 75 is used in the current control unit 7, and the control is performed instead of the control unit 9. That is, the part 9B is used.

  The current control unit 7 shown in FIG. 16 converts the DC voltage output from the PFC circuit 5 into a DC current that can be input to the light source 8 based on the control signal output from the switching control unit 93.

  The current control unit 7 shown in FIG. 16 is composed of a step-down chopper circuit, but in addition to the step-down chopper circuit, a circuit such as a step-up / step-down chopper circuit, flyback circuit, flyforward circuit, SEPIC, Zeta converter, or Cuk converter. It may be composed of.

  The current controller 7 includes a MOSFET 71, a coil 75, a diode 73 and a capacitor 74.

  The coil 75 is arranged between the capacitor 74 and the MOSFET 71 on the DC bus P on the positive electrode side. A primary winding 75a and a secondary winding 75b are formed on the coil 75 by winding an insulating wire around a core (not shown).

  One end of the primary winding 75a is connected to the source of the MOSFET 71 and the cathode of the diode 73. The other end of the primary winding 75a is connected to one end of the capacitor 74 and one end of the light source 8. One end of the secondary winding 75b is connected to the zero current detector 92 in the controller 9B. The other end of the secondary winding 75b is connected to the negative side DC bus N. Voltages having different polarities are applied to the primary winding 75a as the MOSFET 71 is turned on and off. The voltage induced on the secondary winding 75b and generated across the secondary winding 75b is equal to the voltage applied to the primary winding 75a and the voltage according to the turn ratio n.

  The MOSFET 71 is arranged on the DC bus P on the positive electrode side. The drain of the MOSFET 71 is connected to one end of the smoothing capacitor 6. The source of the MOSFET 71 is connected to the cathode of the diode 73 and one end of the primary winding 75 a of the coil 75. The gate of the MOSFET 71 is connected to the switching control unit 93. The control signal output from the switching control unit 93 is input to the gate of the MOSFET 71. The control signal is a signal for on / off controlling the MOSFET 71.

  Next, the operation of the current controller 7 will be described in detail.

  FIG. 17 is a timing chart showing the relationship between the current flowing through the light source, the current flowing through the primary winding, and the control signal of the MOSFET. In FIG. 17, the current flowing through the light source 8, the voltage applied between the drain and the source of the MOSFET 71, the current flowing through the primary winding 75a, the zero current detection signal, and the control signal for the MOSFET 71 are sequentially shown from the top. Shown. In FIG. 17, the voltage applied between the drain and the source is referred to as “drain voltage”. The horizontal axis represents time.

  When the MOSFET 71 is turned on at time t1, a closed circuit is formed by the smoothing capacitor 6, the MOSFET 71, the primary winding 75a and the capacitor 74, and the current flowing through the primary winding 75a increases, and the primary winding 75a, Energy is stored in the capacitor 74.

  At time t2 when the ON time Ton set in the switching control unit 93 has elapsed, the MOSFET 71 is turned off to form a closed circuit of the primary winding 75a, the capacitor 74, and the diode 73. In this closed circuit, the energy stored in the primary winding 75a is released and the capacitor 74 is charged.

  The MOSFET 71 is maintained in the OFF state until the delay time Tdelay elapses from the time t3 when the current flowing through the primary winding 75a becomes zero. At time t4 when the delay time Tdelay has elapsed, the MOSFET 71 is turned on again. That is, the control signal of the MOSFET 71 remains off from the time when the current flowing through the primary winding 75a becomes zero to the time when the delay time Tdelay elapses. Then, when the delay time Tdelay has elapsed, the control signal of the MOSFET 71 changes to the ON state.

  Due to the series of on / off operations of the MOSFET 71, the current flowing through the primary winding 75a has a triangular waveform.

  At this time, the current output from the current controller 7 to the light source 8 is smoothed by the capacitor 74. Therefore, the average value of the current flowing through the primary winding 75a is output to the light source 8. That is, the current output from the current control unit 7 to the light source 8 has a DC waveform in which fluctuations are removed.

  The current detector 11 detects the current flowing through the light source 8 and sends the detected current to the controller 9B. The controller 9B feedback-controls the on-time Ton of the MOSFET 71 so that the current detected by the current detector 11 follows the target value. That is, the control unit 9B lengthens the ON time Ton of the MOSFET 71 when the detected current is smaller than the target value, and shortens the ON time Ton of the MOSFET 71 when the detected current is larger than the target value.

  In the lighting device 100 according to the first embodiment, an example has been shown in which the MOSFET 71 of the current control unit 7 is duty-controlled at a fixed frequency. On the other hand, when the MOSFET 71 is controlled in the current critical mode, the MOSFET 71 operates at a higher switching frequency. Therefore, if the current output to the light source 8 when the MOSFET 71 is controlled in the current critical mode is equal to the current output to the light source 8 when the MOSFET 71 is duty-controlled at a fixed frequency, the current critical mode control is turned on. The time Ton can be shortened. The on-time Ton is determined by the magnitude of the current output to the light source 8, and becomes the longest when all lights are turned on. Further, at this time, the peak value of the current flowing through the primary winding 75a also becomes maximum. The smaller the magnitude of the current flowing through the primary winding 75a, the lower the magnetic flux density generated in the magnetic core forming the coil 75, and the size of the core can be reduced. Therefore, by controlling the MOSFET 71 in the current critical mode. The coil 75 can be miniaturized.

  However, when dimming the light source 8, the switching control unit 93 controls the ON time Ton of the MOSFET 71 to be short in order to reduce the input current of the AC power supply 1. Therefore, in the current critical mode control, the ON time Ton of the MOSFET 71 becomes too short at the time of dimming, the ON / OFF operation of the MOSFET 71 becomes unstable, and flicker may occur in the output light of the light source 8. The flicker of the output light is equal to the fluctuation of the brightness of the light source 8.

  FIG. 18 is a diagram showing the characteristics of the on-time and switching frequency of the MOSFET that change according to the dimming ratio. In FIG. 18, the on time of the MOSFET 71, the switching frequency, and the dimming ratio of the light source 8 are shown in order from the top.

  The dotted line represents the ON time and the switching frequency of the MOSFET 71 when the dimming ratio is changed when the current critical mode control is performed without providing the delay time Tdelay. The solid line represents the ON time and the switching frequency of the MOSFET 71 when the dimming ratio is changed when the delay time Tdelay is provided and the current discontinuous mode control is performed.

  By providing the delay time Tdelay and controlling the MOSFET 71 in the current discontinuous mode control, an increase in the switching frequency during dimming can be suppressed and the switching loss can be reduced as compared with the current critical mode control. Further, the on time of the MOSFET 71 can be lengthened, and the on / off control of the MOSFET 71 can be performed more reliably. In the current control unit 7, if the ON time of the MOSFET 71 becomes too short, the ON / OFF operation of the MOSFET 71 may become unstable, and flicker of output light may occur in the light source 8. Therefore, the delay time Tdelay is set. By providing the light source, the on-time can be secured, and the dimming control can be performed without causing the output light of the light source 8 to flicker. The length of ON time during which the MOSFET 71 cannot normally operate on / off is, for example, 0.2 sec or less. Therefore, the control unit 9B stores the minimum on-time Ton_min, and when dimming the light source 8, the dimming control can be performed so that the on-time of the MOSFET 71 is not shorter than the minimum on-time Ton_min. The minimum on-time Ton_min is equal to the length of on-time during which the MOSFET 71 cannot operate normally on / off.

  From the above, when the delay time Tdelay is provided and the MOSFET 71 is controlled in the discontinuous current mode, the peak current of the primary winding 75a can be reduced as compared with the case where the duty control is performed, as in the case of the current critical mode control. The 75 can be made smaller. Further, as compared with the case where the current critical mode control is performed, it is possible to suppress a decrease in the on-time of the MOSFET 71 when the light source 8 is dimmed, and thus it is possible to suppress flickering in the output light of the light source 8 during dimming.

  If the length of the delay time Tdelay is changed during the period when the light source 8 is turned on, the switching frequency of the MOSFET 71 changes, so the current output to the light source 8 changes and the output of the light source 8 changes. Flickering in the light. Therefore, after the lighting of the light source 8 is started, by making the length of the delay time Tdelay constant regardless of the dimming rate, the switching frequency fluctuation of the MOSFET 71 is suppressed, and the flicker of the output light of the light source 8 is suppressed. It

  FIG. 19 is a first diagram showing the operation of the current controller when the magnitude of the current output to the light source is different. FIG. 20 is a second diagram showing the operation of the current controller when the magnitude of the current output to the light source is different. 19 and 20, in order from the top, the current output to the light source 8, the voltage applied between the drain and source of the MOSFET 71, the current flowing through the primary winding 75a, the zero current detection signal, and the MOSFET 71. Control signals of In FIGS. 19 and 20, the voltage applied between the drain and the source is referred to as “drain voltage”. The horizontal axis represents time.

  When the current output to the light source 8 is reduced by dimming the light source 8, the ON time of the control signal of the MOSFET 71 is shortened. Ton (a) has a relationship of ON time Ton (a) at full light> ON time Ton (b) at dimming. On the other hand, since the length of the delay time Tdelay is constant regardless of the dimming rate, the delay time Tdelay (a) at the time of full light and the delay time Tdelay (b) at the time of dimming are Delay time Tdelay (a) = delay time Tdelay (b) during dimming.

  Further, when the length of the delay time Tdelay is changed while the light source 8 is turned on, a determination means for changing the delay time Tdelay is required. Therefore, for example, when the determination means is implemented by using a computing element such as a microcomputer or a CPU, it is necessary to describe a complicated instruction for determination processing, which increases the memory capacity to be used. Further, when the determination means is realized by using an analog circuit, the number of parts increases and the circuit configuration becomes complicated. Therefore, by making the length of the delay time Tdelay constant irrespective of the dimming rate, it is possible to suppress an increase in the memory capacity of a computing element such as a microcomputer or a CPU, and to suppress an increase in the number of parts constituting an analog circuit. it can.

  As a specific method for providing the delay time Tdelay, the control unit 9B turns on the MOSFET 71 near the bottom of the voltage oscillation of the MOSFET 71 while the drain voltage of the MOSFET 71 is freely oscillating. As a result, abrupt changes in the drain voltage are suppressed, and noise caused by switching is suppressed. Further, among the bottoms of the voltage oscillation of the MOSFET 71 that occur a plurality of times, the control unit 9B turns on the MOSFET 71 at least at the bottom after the second time, so that the delay time Tdelay can be reliably provided.

  The configuration described in the above third embodiment shows an example of the content of the present invention, and can be combined with another known technique, or can be combined with the configuration described in the first embodiment. Is.

  In the third embodiment, the case where the light source 8 is composed of an LED has been described, but the light source 8 is not limited to the LED and may be an organic EL as long as it is dimmable.

Fourth Embodiment
FIG. 21 is a configuration diagram of the lighting device and the lighting fixture according to the fourth embodiment. In the fourth embodiment, parts having the same configurations as those of lighting device 100B and lighting fixture 200B according to the third embodiment of FIG. 16 are designated by the same reference numerals and the description thereof will be omitted.

  The difference between the lighting fixture 200C according to the fourth embodiment and the lighting fixture 200B according to the third embodiment is that the lighting fixture 100C is used in place of the lighting fixture 100B in the lighting fixture 200C. Further, the difference between the lighting device 100C according to the fourth embodiment and the lighting device 100B according to the third embodiment is that in the lighting device 100C, the control unit 9C includes a cycle measuring unit 96, and the control unit 9C has a zero current. This is to measure the detection cycle Tzcd and determine the delay time Tdelay.

  Next, the operation of the cycle measuring unit 96 will be described in detail.

  FIG. 22 is a first timing chart showing the timing of measuring the zero current detection period Tzcd in the period from the state where the light source is turned off to the time when the light source starts to be turned on in the fourth embodiment. In FIG. 22, for convenience of explanation, a cycle in which the gate voltage of the MOSFET 71 is turned on and off is described longer than it actually is. In FIG. 22, in order from the top, the voltage applied to the light source 8, the current flowing through the light source 8, the voltage applied between the drain and source of the MOSFET 71, the current flowing through the primary winding 75a, and the zero current detection. Signals and control signals for MOSFET 71 are shown. In FIG. 22, the voltage applied between the drain and the source is described as “drain voltage”. The horizontal axis represents time.

  The current control unit 7 starts ON / OFF control of the MOSFET 71 from time t1. When an LED is used as the light source 8, no current flows in the light source 8 at the forward voltage threshold Vfth or less, and therefore only the voltage applied to the light source 8 rises during the period from time t1 to t3. The forward voltage threshold Vfth is equal to the voltage at which a current starts flowing through the LED, that is, the voltage at which the LED starts lighting, among the voltages applied to the LED.

  At time t3, when the voltage applied to the light source 8 exceeds the forward voltage threshold Vfth, a current starts flowing through the LED and the LED starts lighting. After the start of lighting of the LED, the current flowing through the light source 8 increases, and when the current flowing through the light source 8 reaches the target value at time t4, the increase in the current flowing through the light source 8 ends, and the current flows through the light source 8 after time t4. The current value becomes constant.

  The maximum value of the voltage generated across the secondary winding 75b can be represented by the product of the turn ratio n of the primary winding 75a and the secondary winding 75b and the voltage applied to the light source 8. Therefore, during the period in which the voltage applied to the light source 8 rises from time t1 to t4, the maximum value of the voltage generated across the secondary winding 75b also rises. At time t2, the cycle measuring unit 96 detects the maximum value of the zero current detection signal while the MOSFET 71 is on. Then, the cycle measuring unit 96 measures the zero current detection cycle Tzcd after the MOSFET 71 is turned off when the maximum value of the detected zero current detection signal reaches the cycle detection threshold value Though, and information on the measured zero current detection cycle Tzcd. To the switching control unit 93C.

  When the switching control unit 93C receives the information regarding the zero current detection period Tzcd from the period measurement unit 96, the switching control unit 93C determines the delay time Tdelay based on the zero current detection period Tzcd. A method of determining the delay time Tdelay will be described later.

  The zero current detection period Tzcd is calculated by comparing the parasitic capacitance of the MOSFET 71, the inductance of the primary winding 75a, the parasitic capacitance of the LED used as the light source 8, the wiring parasitic capacitance of the lighting device 100C, and the wiring parasitic inductance of the lighting device 100C. It changes depending on the size. Therefore, the cycle measuring unit 96 measures the zero current detection period Tzcd, and the switching control unit 93C determines the delay time Tdelay based on the zero current detection period Tzcd, so that the bottom of the drain voltage free oscillation of the MOSFET 71 is more accurately determined. The MOSFET 71 can be turned on at the timing.

  As a result, a sharp change in the drain voltage of the MOSFET 71 is suppressed, noise caused by switching is suppressed, and the noise filter circuit can be downsized.

  As a method of determining the delay time Tdelay, a method of setting the delay time Tdelay to be n times as long as the zero current detection period Tzcd can be considered. n is a value exceeding 1. For example, by setting the delay time Tdelay to be 1.5 times as long as the zero current detection period Tzcd, the MOSFET 71 can be turned on at the bottom timing of the free oscillation of the drain voltage of the MOSFET 71.

  If the delay time Tdelay is changed after the time t3 when the light source 8 is turned on, the current output to the light source 8 fluctuates and the output light of the light source 8 flickers. Therefore, the cycle detection threshold value Sith is provided so that the time t2 when the zero current detection cycle Tzcd is measured is before the time t3 when the light source 8 starts lighting.

  Up to this point, the configuration example in which the maximum value of the zero current detection signal is used to determine the time for the period measurement unit 96 to measure the zero current detection period Tzcd has been described, but the voltage applied to the light source 8 is described. May be detected, and the time at which the zero current detection period Tzcd is measured may be determined using the detected voltage. Also in this case, the voltage threshold applied to the light source 8 can be provided so that the time t2 at which the zero current detection period Tzcd is measured is before the time t3 at which the light source 8 starts lighting. However, in this case, the illumination device 100C needs to be provided with a voltage detection unit for detecting the voltage applied to the light source 8.

  FIG. 23 is a second timing chart showing the timing of measuring the zero current detection period Tzcd in the period from the state where the light source is turned off to the time when the light source starts to be turned on in the fourth embodiment. In FIG. 23, in order from the top, the voltage applied to the light source 8, the current flowing through the light source 8, the voltage applied between the drain and source of the MOSFET 71, the current flowing through the primary winding 75a, and the zero current detection. Signals and control signals for MOSFET 71 are shown. In FIG. 23, the voltage applied between the drain and the source is referred to as “drain voltage”. The horizontal axis represents time.

  The current control unit 7 starts ON / OFF control of the MOSFET 71 from time t1. When an LED is used as the light source 8, no current flows in the light source 8 at the forward voltage threshold Vfth or less, and therefore only the voltage applied to the light source 8 rises during the period from time t1 to t3.

  When the voltage applied to the light source 8 exceeds the forward voltage threshold Vfth at time t3, a current starts flowing through the LED, and the LED starts lighting. After the start of lighting, the current flowing through the light source 8 increases, and when the current flowing through the light source 8 reaches the target value at time t4, the increase in the current flowing through the light source 8 ends, and the value of the current flowing through the light source 8 after time t4. Is constant.

  The switching control section 93C causes the cycle measuring section 96 to start the zero current detection cycle measurement when the current detected by the current detecting section 11 reaches the target value. That is, the switching control unit 93C requests the period measuring unit 96 to start measuring the zero current detection period.

  When the cycle measuring unit 96 receives a request for starting the measurement of the zero current detection period from the switching control unit 93C, the MOSFET 71 is turned off, then the zero current detection period Tzcd is measured, and the information on the measured zero current detection period Tzcd is controlled by switching. It is transmitted to the section 93C.

  Upon receiving the information about the zero current detection period Tzcd from the period measurement unit 96, the switching control unit 93C calculates the delay time Tdelay based on the zero current detection period Tzcd. The calculation result of the delay time Tdelay is reflected when the light source 8 is turned off and then the light source 8 is turned on again.

  As described above, the zero current detection period Tzcd is determined by the parasitic capacitance of the MOSFET 71, the inductance of the primary winding 75a, the parasitic capacitance of the LED used as the light source 8, the wiring parasitic capacitance of the lighting device 100C, and the lighting device 100C. Changes depending on the size of the wiring parasitic inductance. In particular, the parasitic capacitance of the MOSFET has a characteristic that depends on the magnitude of the drain voltage. Therefore, by determining the delay time Tdelay based on the zero current detection period Tzcd measured while the light source 8 is on, the MOSFET 71 is turned on more accurately at the bottom timing of the drain voltage free oscillation of the MOSFET 71. be able to.

  The parasitic capacitance of the MOSFET changes depending on the magnitude of the drain voltage. Further, the oscillation cycle of the drain voltage changes depending on the parasitic capacitance of the MOSFET. From these, it can be said that the oscillation cycle of the drain voltage changes depending on the magnitude of the drain voltage. The following method is a simple method for determining the delay time Tdelay when the zero current detection period Tzcd changes. In the first method, the length of the delay time Tdelay corresponding to the voltage applied to the light source 8 is determined in advance, the voltage applied to the light source 8 during the lighting operation is detected, and the detected voltage is applied. This is a method of determining the delay time Tdelay. That is, this is a method of changing the delay time Tdelay according to the voltage applied to the light source 8. In the second method, the length of the delay time Tdelay corresponding to the input voltage of the current control unit 7 is set in advance, the voltage input to the current control unit 7 during the lighting operation is detected, and the detected voltage is set to the detected voltage. This is a method of determining the corresponding delay time Tdelay. That is, there is a method of changing the delay time Tdelay according to the input voltage of the current control unit 7.

  As a result, a sharp change in the drain voltage of the MOSFET 71 is suppressed, noise caused by switching is suppressed, and the noise filter circuit can be downsized.

  As a method of determining the delay time Tdelay, a method of setting the delay time Tdelay to be n times as long as the zero current detection period Tzcd can be considered. n is a value exceeding 1. For example, by setting the delay time Tdelay to be 1.5 times as long as the zero current detection period Tzcd, the MOSFET 71 can be turned on at the bottom timing of the free oscillation of the drain voltage of the MOSFET 71.

  If the delay time Tdelay is changed after the time t3 when the light source 8 is turned on, the current output to the light source 8 fluctuates and the output light of the light source 8 flickers. Therefore, by reflecting the delay time Tdelay calculated from the zero current detection period Tzcd immediately before the light source 8 is turned on again after being turned off, it is possible to suppress the flicker of the output light of the light source 8.

  Next, the control in the case where the delay time Tdelay is calculated after the light source 8 is turned on and the delay time Tdelay is reflected after the light source 8 is turned off will be described in more detail using the flowchart of FIG. FIG. 24 is a flowchart showing the operation of the lighting device according to the fourth embodiment.

  When the light source 8 is in the off state, the control unit 9C waits for the input of the lighting command of the light source 8 until the lighting command of the light source 8 is input (S301, S302: No).

  When the lighting command for the light source 8 is input (S302: Yes), the control unit 9C updates the delay time Tdelay (S303). When the update of the delay time Tdelay is completed, the control unit 9C causes the switching control unit 93C to start the on / off operation of the MOSFET 71, whereby the current control unit 7 starts the operation (S304).

  Next, the switching control unit 93C determines whether or not the current detected by the current detection unit 11 has reached the target value. When the current flowing through the light source 8 has not reached the target value, that is, when the value of the current flowing through the light source 8 is less than the target value (S305: Yes), the process of S305 is repeated and the cycle measuring unit 96 does not operate. .. That is, the zero current detection period Tzcd is not measured.

  When the current flowing through the light source 8 reaches the target value, that is, when the value of the current flowing through the light source 8 exceeds the target value (S305: No), the cycle measuring unit 96 measures the zero current detection cycle Tzcd (S306). .. Information regarding the zero current detection period Tzcd is transmitted to the switching control unit 93C.

  The switching control unit 93C that has received the information regarding the zero current detection period Tzcd calculates the delay time Tdelay based on the zero current detection period Tzcd, and holds the calculated delay time Tdelay (S307). In addition, when the lighting device 100C operates for the first time, a predetermined delay time Tdelay is set as an initial value.

  When the turn-off command for the light source 8 has not been input (S308: No), the lighting device 100C continues the lighting state of the light source 8 (S309) and performs the process of S308. When the turn-off command for the light source 8 is input (S308: Yes), the lighting device 100C turns off the light source 8 (S310), and the lighting device 100C waits for the input of the turn-off command.

  The configuration described in the above fourth embodiment shows an example of the content of the present invention, and can be combined with another known technique or can be combined with the configuration described in the first embodiment. Is.

  In the fourth embodiment, the case where the light source 8 is composed of an LED has been described, but the light source 8 is not limited to an LED and may be an organic EL as long as it is dimmable.

  In the present embodiment, an example in which the length of the delay time is determined according to the value of the output current measured by the current detection unit 11 has been described, but instead of the current detection unit 11, the output of the DC conversion circuit 30 is output. An output voltage detection unit that detects the voltage or an input voltage detection unit that detects the input voltage of the DC conversion circuit 30 may be used. Even if the delay time length is determined according to the output voltage detected by the output voltage detection unit, or the delay time length is determined according to the input voltage detected by the input voltage detection unit, The effect of is obtained.

  The configurations described in the above embodiments show an example of the content of the present invention, and can be combined with another known technique, and the configurations of the configurations are possible without departing from the gist of the present invention. It is also possible to omit or change parts.

  1 AC power supply, 2 input filter, 3 rectifier circuit, 4,22,74 capacitor, 5 PFC circuit, 6,124 smoothing capacitor, 7 current control unit, 8 light source, 9,9A, 9B, 9C control unit, 10 dimming Device, 11 current detection unit, 12, 30 DC conversion circuit, 21, 52, 72, 75 coil, 51, 71, 121 MOSFET, 52a, 75a, 122a primary winding, 52b, 75b, 122b secondary winding, 53, 73, 123 diode, 91 target value output section, 92 zero current detection section, 93, 93A, 93C switching control section, 94 current input section, 95 voltage detection section, 96 cycle measurement section, 100, 100A, 100B, 100C Lighting device, 122 transformer, 122c tertiary winding, 125 snubber capacitor, 126 snubber resistor, 127 snubber Diode, 200, 200A, 200B, 200C Lighting equipment.

Claims (19)

A rectifier circuit that rectifies AC power;
A DC conversion circuit that suppresses harmonics to improve the power factor and converts the power output from the rectifier circuit to DC power and supplies the DC power to the light source,
And a control unit for controlling the DC conversion circuit,
The DC conversion circuit includes a smoothing capacitor, a switching element arranged between the smoothing capacitor and the rectifier circuit, and a coil through which a current output from the rectifier circuit flows.
The control unit keeps the switching element in the off state until the delay time set in the control unit elapses from the time when the current flowing through the coil becomes zero, and when the delay time elapses, Turn on the switching element,
The control unit keeps the length of the delay time constant in a state where the light source is turned on,
The control unit includes a cycle measuring unit that measures a cycle in which a current flowing through the coil becomes zero,
The said control part is a lighting device which determines the length of the said delay time according to the said period measured by the said period measurement part. A rectifier circuit that rectifies AC power;
A DC conversion circuit that suppresses harmonics to improve the power factor and converts the power output from the rectifier circuit to DC power and supplies the DC power to the light source,
And a control unit for controlling the DC conversion circuit,
The DC conversion circuit includes a smoothing capacitor, a switching element arranged between the smoothing capacitor and the rectifier circuit, and a coil through which a current output from the rectifier circuit flows.
The control unit keeps the switching element in the off state until the delay time set in the control unit elapses from the time when the current flowing through the coil becomes zero, and when the delay time elapses, Turn on the switching element,
The control unit keeps the length of the delay time constant in a state where the light source is turned on,
The control unit changes the length of the delay time in a state where the light source is turned off,
The control unit includes a cycle measuring unit that measures a cycle in which a current flowing through the coil becomes zero,
The said control part is a lighting device which determines the length of the said delay time according to the said period measured by the said period measurement part. A rectifier circuit that rectifies AC power;
A DC conversion circuit that suppresses harmonics to improve the power factor and converts the power output from the rectifier circuit to DC power and supplies the DC power to the light source,
And a control unit for controlling the DC conversion circuit,
The DC conversion circuit includes a smoothing capacitor, a switching element arranged between the smoothing capacitor and the rectifier circuit, and a coil through which a current output from the rectifier circuit flows.
The control unit keeps the switching element in the off state until the delay time set in the control unit elapses from the time when the current flowing through the coil becomes zero, and when the delay time elapses, Turn on the switching element,
The control unit changes the length of the delay time in a state where the light source is turned off,
The control unit includes a cycle measuring unit that measures a cycle in which a current flowing through the coil becomes zero,
The said control part is a lighting device which determines the length of the said delay time according to the said period measured by the said period measurement part. The said control part is a lighting device as described in any one of Claim 1 to 3 which changes the length of the said delay time according to the magnitude | size of the output of the said DC conversion circuit. The control unit provides a plurality of thresholds for the magnitude of the output, and controls the switching element using a plurality of the delay times having different lengths according to a range between adjacent thresholds. The lighting device according to item 4 . Wherein, in a period in which turning off the switching element, according to any one of claims 1 to 5 for turning on said switching element at a timing when voltage oscillation is of the second and subsequent bottom of the switching element Lighting device. The control section provides a minimum on-time of the switching element, and changes the length of the delay time according to the magnitude of the output, thereby operating the switching element with an on-time of the minimum on-time or more. The lighting device according to any one of claims 4 to 6 . The lighting device according to any one of claims 4 to 7 , wherein the control unit changes the length of the delay time by providing a maximum variation amount of the delay time in a preset maintenance time. It said light source lighting device according to any one of constituted claims 1 to 8 in LED. The lighting device according to claim 9 , wherein the magnitude of the output is determined by a dimming rate of the LED. The lighting device according to claim 9 , wherein the magnitude of the output is determined by an output current target value of the LED. It said light source lighting device according to any one of constituted claims 1 to 8 in an organic EL. The size of the output, the lighting device according to claim 1 2, which is determined by the dimming ratio of the organic EL. The lighting device according to claim 3 , wherein the control unit keeps the length of the delay time constant while the light source is turned on. The cycle measuring unit measures the cycle after the DC conversion circuit starts operating and before the light source is turned on,
Wherein, in response to said measured period, the lighting device according to any one of claims 1 to 3, changing the length of the delay time. The cycle measuring unit measures the cycle after the light source is turned on after the DC conversion circuit starts operating,
The lighting device according to claim 3 , wherein the control unit changes the length of the delay time after turning off the light source according to the measured cycle. Wherein the control unit includes an output voltage detection unit for detecting an output voltage of the DC conversion circuit, in response to the output voltage, the lighting device according to claim 1 4 which determines the length of the delay time. Wherein the control unit comprises an input voltage detection unit for detecting an input voltage of the DC conversion circuit, in response to the input voltage, the lighting device according to claim 1 4 which determines the length of the delay time. A lighting fixture comprising the lighting device according to any one of claims 1 to 18 .

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