WO2018235199A1

WO2018235199A1 - Light source lighting device and illumination apparatus

Info

Publication number: WO2018235199A1
Application number: PCT/JP2017/022880
Authority: WO
Inventors: 雄一郎伊藤; 岳秋飯田; 信一芝原
Original assignee: 三菱電機株式会社; 三菱電機照明株式会社
Priority date: 2017-06-21
Filing date: 2017-06-21
Publication date: 2018-12-27
Also published as: JP6725075B2; CN110809909A; CN110809909B; JPWO2018235199A1

Abstract

The invention is characterized by including a rectifier circuit for rectifying an alternating current power source, a power factor correction circuit into which the output from the rectification circuit enters and from which a direct current voltage exits that has a switching element and an inductor, a detector coil for detecting the voltage arising at the inductor, and a control unit into which the voltage detected by the detector coil is input and which drives the switching element, wherein after a first off-period has elapsed, from when the switching element has been turned-off to when the oscillation voltage of the detector coil has dropped at least twice, the control unit maintains the off-state of the switching element until a pre-defined second off-period elapses, and, after the second off-period has elapsed, turns-on the switching element.

Description

Light source lighting device, lighting equipment

The present invention relates to a light source lighting device and a luminaire using the same.

Conventionally, various light source lighting devices for lighting light emitting elements such as light emitting diodes are known. This type of light source lighting device comprises an AC-DC conversion circuit that rectifies and smoothes commercial AC power to generate a DC voltage, and DC- that supplies an optimal current to a light emitting diode from the DC voltage obtained from the conversion circuit. It has a DC converter. A high power factor is required in many luminaires. Therefore, as shown in Patent Document 1, a two-converter system using a step-up chopper type power factor improvement circuit as an AC-DC conversion circuit and a step-down chopper circuit as a DC-DC converter is widely adopted.

In this case, as described in paragraph 0085 of the specification of Patent Document 2, it is general to operate the step-up chopper type power factor correction circuit in the current critical mode. In the current critical mode, zero current detection is performed to detect that the current of the choke coil has become zero after the switching element is turned off, and the next switching is started immediately after the zero current detection. In the current critical mode, when the brightness of the light source is reduced by the dimming function to adjust the brightness of the light source, the load is light and the on / off time of the switching element is shortened and the switching frequency is increased. Along with this, the switching loss is increased or the frequency of the switching element can be exceeded, which causes the circuit operation to become unstable. As a result, there is a problem that a decrease in power factor and flicker of a light source occur.

Therefore, Patent Document 3 discloses a method of suppressing the rise of the switching frequency and operating stably by delaying the timing of turning on the switching element and operating in the current discontinuous mode.

Japanese Unexamined Patent Publication No. 2010-040400 Japanese Patent Application Laid-Open No. 2001-313423 Japanese Patent Application Laid-Open No. 2016-119830

In the specification paragraphs 0039 to 0043 of Patent Document 3, the frequency reduction operation by the current discontinuous mode is disclosed. Specifically, based on the input timing of the output signal of the zero current detector, the turn-on timing of the switching element is controlled through the delay time corresponding to the control signal indicating the load state, and the frequency reduction control at light load is executed. Be done.

The current discontinuous mode control described in Patent Document 3 turns on the switching element after a predetermined delay time has elapsed with reference to the input timing of the output signal of the zero current detector. During the delay time in which the switching element is off, the stray capacitance between the inductor of the power factor correction circuit and the electrode of the switching element causes resonant operation. With this resonance operation, a minute oscillating current flows through the switching element. When a predetermined delay time has elapsed and the switching element is turned on, this oscillating current is superimposed on the inductor current.

When, for example, a MOSFET is used as a switching element, the stray capacitance between the electrodes depends on the drain-source voltage. Therefore, for example, when the drain-source voltage changes due to the phase angle of the AC power supply voltage, the frequency of the resonant operation fluctuates. If the on time of the switching element is approximately constant during a half cycle of the AC power supply, the value of the oscillating current superimposed on the inductor current will differ depending on the phase of the power supply. That is, during the half cycle of the AC power supply, a large oscillating current is superimposed on the inductor current at a certain timing, and almost no oscillating current is superimposed on the inductor current at another timing. In this case, assuming that the on-time of the switching element is substantially constant, the envelope indicated by the peak value of the sum of the inductor current and the oscillating current does not become sinusoidal, and the power factor is lowered.

In order to suppress such a reduction in power factor, the current flowing through the switching element is monitored every switching cycle, and the switching element is turned on so that the peak value of the sum of the inductor current and the oscillating current superimposed thereon is sinusoidal. You have to control the time. For example, in order to realize such control with a microcomputer, it is necessary to calculate the on-time at very short intervals, which is computationally expensive.

The present invention has been made to solve the above-mentioned problems, and it is possible to provide a light source lighting device and a luminaire which can determine the off period of the switching element by a simple control method and can suppress the reduction in power factor. To aim.

A light source lighting device according to the invention of the present application includes a rectifier circuit that rectifies AC power, a switching element and an inductor, a power factor improvement circuit that receives an output of the rectifier circuit and outputs a DC voltage, and the inductor And a control unit that receives the voltage detected by the detection winding and drives the switching element, and the control unit turns the switching element off. After the first off period until the oscillating voltage of the detection winding falls at least twice, the off state of the switching element is continued until the predetermined second off period elapses, and the second off period The switching element is turned on after the lapse of time.

A lighting fixture according to the invention of this application includes a rectifier circuit that rectifies an AC power supply, a switching element and an inductor, a power factor improvement circuit that receives an output of the rectifier circuit and outputs a DC voltage, and the inductor The control unit includes a detection winding that detects a voltage to be generated, and a control unit that receives the voltage detected by the detection winding and drives the switching element, and the control unit turns the switching element off before the control unit turns off the switching element. After lapse of the first off period until the oscillating voltage of the detection winding falls at least twice, the switching element continues to be in the off state until a predetermined second off period elapses, during the second off period. A light source lighting device characterized in that the switching element is turned on after lapse of time, and an LED or an organic EL which is turned on by the light source lighting device.

Other features of the present invention will be clarified below.

According to the present invention, after detecting the second and subsequent falling of the oscillating voltage generated after the current of the inductor becomes zero after the switching element is turned off, the switching element is selected after a predetermined delay time has elapsed. Turn on. As a result, the rate of delay time during turn-off can be reduced while suppressing an increase in switching frequency, so distortion of the input current waveform can be reduced and a decrease in power factor can be prevented.

FIG. 1 is a circuit configuration diagram of a light source lighting device according to a first embodiment. FIG. 5 is a waveform chart showing an operation in a steady state of the light source lighting device according to Embodiment 1. FIG. 6 is a waveform diagram showing a power factor improvement operation of the light source lighting device according to Embodiment 1. It is a wave form diagram of the voltage between drain sources, and the electric current of an inductor. It is a wave form diagram which shows that oscillating current was superimposed on inductor current. It is a flowchart which shows the sequence of a process. It is a figure which shows the update timing of on time. It is a block diagram of a control part realized by hardware. It is a block diagram of a control part realized by software. FIG. 13 is a diagram showing correspondence between a light source current and an off time of a switching element according to the second embodiment. It is a figure which shows the operation | movement waveform in case the upper limit fall frequency | count of oscillating voltage is 3 times. FIG. 7 is a cross-sectional view of a lighting fixture according to Embodiment 3.

A light source lighting device and a lighting fixture according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components may be assigned the same reference numerals and repetition of the description may be omitted.

Embodiment 1
FIG. 1 is a circuit diagram of a light source lighting device 100 according to a first embodiment of the present invention. The light source lighting device 100 receives the supply of power from the AC power supply 1 to light the light source 9. A configuration in which the light source 9 is added to the light source lighting device 100 is referred to as a lighting fixture. The light source 9 of the first embodiment is not particularly limited, but is, for example, a light emitting diode (LED). The light source lighting device 100 includes a rectifier circuit 2, a power factor correction circuit 3, a DC-DC converter 4, a controller 5, a DC-DC converter controller 7, and a dimming signal interface 8. The rectifier circuit 2 rectifies AC power. Specifically, the AC voltage input from the AC power supply 1 is full-wave rectified. The full-wave rectified voltage is not smoothed during the operation of the power factor correction circuit 3 and becomes a ripple voltage including a frequency twice that of the AC power supply 1.

A power factor improvement circuit 3 is connected to the rectifier circuit 2. The power factor correction circuit 3 includes a filter capacitor C1, an inductor L1, for example, a switching element SW1 formed of a MOSFET, a diode D1, and a smoothing capacitor C2. The power factor correction circuit 3 is a boost chopper circuit configured by these circuit elements. That is, in order to supply a direct current to the light source 9 through the DC-DC converter 4, the power factor improvement circuit 3 charges and discharges energy with the switching element SW1 and the inductor L1 to generate a desired DC voltage. That is, the power factor correction circuit 3 includes the switching element SW1 and the inductor L1, receives the output of the rectifier circuit 2, and outputs a DC voltage.

A detection winding L2 is magnetically coupled to the inductor L1. That is, the detection winding L2 is provided in the inductor L1. Specifically, it is preferable to wind the detection winding L2 around a ferromagnetic material around which the inductor L1 winds. The detection winding L2 detects a voltage generated in the inductor L1. The power factor correction circuit 3 includes a power supply voltage detection unit R1 and an output voltage detection unit R2. The power supply voltage detection unit R1 is a voltage dividing circuit that divides a power supply voltage by two resistance elements connected in series. The output voltage detection unit R2 is a voltage dividing circuit that divides the output voltage of the power factor correction circuit 3 by two resistance elements connected in series. A DC-DC converter 4 for supplying a current to the light source 9 is connected to the output of the power factor correction circuit 3.

The power factor improvement circuit 3 operates under the control of the control unit 5. The power factor correction circuit 3 boosts the voltage full-wave rectified by the rectification circuit 2 and smoothes the DC voltage. Further, the power factor improvement circuit 3 operates so that the input current waveform has a sine wave shape and the same phase as the voltage of the AC power supply 1 under the control of the control unit 5, and performs the power factor improvement.

The control unit 5 drives the switching element SW1. The control unit 5 includes an output voltage detection unit 5a, a drive unit 5b, a delay time setting unit 5c, a power supply voltage detection unit 5d, and an oscillating voltage detection unit 5e. The control unit 5 determines that the voltage of the smoothing capacitor C2, which is the output voltage of the power factor correction circuit 3, is a preset voltage value, and the input current waveform of the light source lighting device 100 has substantially the same phase and sine wave as the voltage of the AC power supply 1. The switching element SW1 is driven such that

Output voltage detection unit 5a is a signal generated in output voltage detection unit R2 formed of a voltage dividing resistor provided inside power factor correction circuit 3, and target signal E1 corresponding to the output voltage target value of power factor improvement circuit 3. And a signal corresponding to the difference between the two. The driver 5b receives the signal from the output voltage detector 5a, determines the on time of the switching element SW1, and drives the switching element SW1.

In the detection winding L2, after the switching element SW1 is turned off, a voltage proportional to the oscillating voltage generated by the interelectrode capacitance of the inductor L1 and the switching element SW1 is generated. The control unit 5 receives the voltage detected by the detection winding L2. The voltage generated in the detection winding L2 is converted by the oscillating voltage detection unit 5e and input to the delay time setting unit 5c. The delay time setting unit 5c counts the number of oscillations until the oscillation voltage input via the oscillation voltage detection unit 5e falls a predetermined number of times. At this time, the delay time setting unit 5c continues the off state of the switching element SW1. When the oscillating voltage falls by a predetermined number of times, delay time setting unit 5c outputs a command to further continue turning off of switching element SW1 for a predetermined delay time from that point to driving unit 5b. When the delay time passes, the delay time setting unit 5c turns on the switching element SW1 via the drive unit 5b.

The dimming controller 10 is provided outside the light source lighting device 100 in order to control the brightness of the light source 9. A dimming signal from the dimming controller 10 is read by the dimming signal interface 8. Then, the dimming signal interface 8 outputs a signal corresponding to the target current value to the DC-DC converter control unit 7 and the delay time setting unit 5c. The delay time setting unit 5c determines the number of falling times and the delay time of the above-mentioned oscillating voltage in accordance with the target current value signal output from the dimming signal interface 8.

The power supply voltage detection unit 5d detects the full-wave rectified voltage divided by the power supply voltage detection unit R1 and detects the phase of the power supply voltage. The power supply voltage detection unit 5d updates the ON time of the switching element SW1 according to the state of the output voltage when the power supply voltage phase determined in advance, for example, near the zero cross point. In the present embodiment, the on-time of the switching element SW1 is updated once in a half cycle of the AC power supply voltage, and the on-time of the previous updating is maintained in the other periods.

The DC-DC converter 4 is driven by a DC-DC converter control unit 7. The DC-DC converter 4 receives the target current value signal output from the dimming signal interface 8 and is constant current feedback controlled so that the light source current becomes the target current value. The detailed configuration of the DC-DC converter 4 is not shown, but any known DC-DC converter can be employed. For example, the DC-DC converter 4 can be configured by a step-down chopper circuit or a flyback converter.

Next, the operation of the light source lighting device 100 according to the first embodiment will be described. When the AC power supply 1 is applied to the light source lighting device 100, the rectifier circuit 2 full-wave rectifies the inputted AC voltage, and the rectified voltage is applied to both ends of the filter capacitor C1. The filter capacitor C1 is provided for the purpose of removing switching ripples, and is not for smoothing the power supply frequency component of the full-wave rectified waveform here. Therefore, the voltage across the filter capacitor C1 during the operation of the power factor correction circuit 3 is a full-wave rectified voltage that pulsates sinusoidally at a frequency twice that of the AC power supply frequency.

The operation of the power factor correction circuit 3 in the steady operation state will be described. When the switching element SW1 is turned on by the drive unit 5b, a full-wave rectified voltage is applied to the inductor L1, current is supplied from the power supply side through the path of the inductor L1 and the switching element SW1, and energy is stored in the inductor L1. At this time, the current of the inductor L1 increases.

When the on time of the switching element SW1 set by the drive unit 5b elapses, the switching element SW1 is turned off. When the switching element SW1 is turned off, the energy stored in the inductor L1 is released, and current flows in the order of the inductor L1, the diode D1, and the smoothing capacitor C2. Thereby, the smoothing capacitor C2 is charged. By thus transferring energy, the DC-DC converter 4 supplies a current to the light source 9 with the voltage charged in the smoothing capacitor C2 as an input.

FIG. 2 is a waveform diagram showing an operation in a steady state of the light source lighting device 100 according to the first embodiment of the present invention. The operation of the control unit 5 will be described with reference to the waveform diagram of FIG.

(Period t0 to t1)
During this period, the switching element SW1 is turned on by the drive unit 5b. When the switching element SW1 is turned on, the current of the inductor L1 flows through the switching element SW1.

Since the current of the inductor L1 increases during this period, the current flowing to the switching element SW1 also increases. At this time, the voltage VL1 is applied to the inductor L1 in the direction of the arrow in FIG. 1, and therefore, a voltage VL2 is generated in the direction of the arrow on the detection winding L2. Both arrows mean that the potential is higher on the end point side than on the start point side. Therefore, a negative voltage is input from the detection winding L2 to the oscillating voltage detection unit 5e. The oscillating voltage detection unit 5e converts a voltage generated in the detection winding L2 into a voltage or the like suitable for inputting to the delay time setting unit 5c. For example, when the delay time setting unit 5c is configured by a microcomputer, the oscillating voltage detection unit 5e is configured by a circuit for waveform shaping or the like so that a negative voltage or an overvoltage is not input to the microcomputer. As shown in FIG. 2, preferably, the oscillating voltage detection unit 5 e outputs an oscillating voltage signal Vs in which the negative voltage is cut.

(Time t1)
When a predetermined time elapses and time t1 is reached, the drive unit 5b turns off the switching element SW1 and cuts off the current of the switching element SW1. The on time of the switching element SW1 is determined by the output voltage detection unit 5a.

(Period t1 to t2)
When the switching element SW1 is turned off at time t1, the energy stored in the inductor L1 is released to the smoothing capacitor C2 via the diode D1. At this time, the voltage generated in the inductor L1 is a voltage reverse to that when the switching element SW1 is on. That is, in the inductor L1, a voltage in the reverse direction to the voltage VL1 shown by the arrow in FIG. 1 is generated. As a result, the voltage generated in the detection winding L2 is also a voltage in the reverse direction to the arrow in FIG. When the switching element SW1 is turned off, the current flowing to the smoothing capacitor C2 gradually decreases, and the current of the inductor L1 becomes zero when the energy release ends.

(Time t2 to t3)
Time t2 is a time at which the inductor current IL1 becomes zero. When the inductor current IL1 becomes zero, the diode D1 is turned off, and a resonant operation occurs between the inductor L1 and the interelectrode capacitance of the switching element SW1. This resonant operation generates an oscillating voltage in the inductor L1. Along with this, an oscillating voltage is also generated in the detection winding L2. The voltage generated in the detection winding L2 is input to the delay time setting unit 5c via the oscillating voltage detection unit 5e.

The delay time setting unit 5c counts the number of falling of the oscillating voltage output from the oscillating voltage detection unit 5e. The number of falling of the oscillating voltage counted by the delay time setting unit 5c is not particularly limited as long as it is at least two, but here, the case of counting twice will be described. The delay time setting unit 5c maintains the off state of the switching element SW1 while counting the number of falling times of the oscillating voltage.

(Time t3 to t4)
At time t3, the number of falling of the oscillating voltage signal Vs reaches a predetermined number. That is, the number of falling times is two. The delay time setting unit 5c further maintains the switching element SW1 in the OFF state for a predetermined delay time from that point on. In the present embodiment, when the number of falling of the oscillating voltage is set to 2 and the second falling of the oscillating voltage is detected, the delay time setting unit 5c starts counting the delay time from that point. As shown in FIG. 2, a period from when the switching element SW1 is turned off to when the falling of the oscillating voltage reaches a predetermined number of times is referred to as a first off period. The delay time provided after the first off period is the second off period.

(Time t4 to t5)
The delay time setting unit 5c gives the drive unit 5b an instruction signal to turn on the switching element SW1 when the delay time has elapsed. Then, the drive unit 5b turns on the switching element SW1 to turn on the switching element SW1. Thus, the next switching cycle is started. In the present embodiment, the delay time is preset so that the switching element SW1 is turned on at a position where the drain-source voltage Vds of the switching element SW1 is at the bottom of the vibration. This can reduce switching loss and noise.

Here, the control of the charging voltage of the smoothing capacitor C2, which is the output voltage of the power factor correction circuit 3, will be described. If the voltage generated by the output voltage detection unit R2 is higher than the target signal E1, the output voltage detection unit 5a outputs, to the drive unit 5b, a signal that shortens the on time of the switching element SW1. In response to this, the drive unit 5b reduces the on time of the switching element SW1 and reduces the output voltage of the power factor correction circuit 3.

On the other hand, if the voltage generated by the output voltage detection unit R2 is lower than the target signal E1, the output voltage detection unit 5a outputs a signal that increases the on time of the switching element SW1 to the drive unit 5b. In response to this, the drive unit 5b increases the on time of the switching element SW1 and increases the output voltage of the power factor correction circuit 3. The drive unit 5b receives the signal from the output voltage detection unit 5a and updates the on time of the switching element SW1. With regard to the timing of this update, the power supply voltage detection unit 5d detects the timing when the power supply voltage phase is near the zero cross, and the drive unit 5b receives this phase detection signal from the power supply voltage detection unit 5d, and switching elements at that timing. It is preferable to update the on time of SW1.

When the current of the light source 9 decreases due to light adjustment, the load becomes a light load and the output voltage of the power factor correction circuit 3 easily increases, so the on time of the switching element SW1 becomes short. When the on time of the switching element SW1 is shortened, the energy discharge time of the inductor L1 is also shortened, so that the switching frequency is increased. An increase in switching frequency causes negative effects such as an increase in switching loss. Therefore, in the present embodiment, in order to suppress the rise of the switching frequency, at the time of light load, the number of falling times of the oscillating voltage of detection winding L2 reaches a predetermined number, and thereafter, until the delay time elapses, The switching element SW1 is turned off. Therefore, an increase in switching frequency can be suppressed.

Next, the power factor improvement operation will be described. FIG. 3 is a waveform diagram showing a power factor improvement operation of the light source lighting device 100 according to the first embodiment of the present invention. When the switching element SW1 is turned on, the current IL1 of the inductor L1 is proportional to the instantaneous value E of the full-wave rectified voltage and inversely proportional to the inductance of the inductor L1, and the slope of E / L1 is approximately proportional to the on time It will rise linearly.

As described above, since the on time of the switching element SW1 is updated near the zero crossing of the power supply voltage phase, the on time t (ON) of the switching element SW1 during a half cycle of the AC power supply becomes a fixed value. That is, the plurality of switchings of the switching element SW1 performed in the half cycle period of the AC power supply have the same on time. Therefore, when the full-wave rectified AC power supply 1 is operated for a half cycle of the waveform of the AC power supply 1, the inductance of the inductor L1 has a constant value, and the peak value of the current of the inductor L1 in each switching cycle is proportional to the power supply voltage. Therefore, as shown in FIG. 3, the envelope of the peak value has a sinusoidal waveform. Then, by removing the switching ripple of the inductor current by the filter capacitor C1 and averaging it, the input current flowing from the AC power supply 1 can be made closer to a sine wave and can be made approximately in phase with the AC power supply voltage. Therefore, the power factor can be improved and the harmonics can be reduced. A filter circuit may be added to the AC input side of the rectifier circuit 2 as necessary.

As described above, the power factor can be improved and the harmonics can be reduced by setting the on time t (ON) of the switching element SW1 to a constant value during a half cycle of the AC power supply. However, distortion may be generated in the input current waveform only by setting the on time to a constant value in a half cycle of the AC power supply, and the power factor may not be improved, so the principle in such a case will be described.

In FIG. 2, when the current IL1 of the inductor L1 reaches zero at time t2 and the switching element SW1 is maintained in the OFF state as it is, the current IL1 is illustrated as maintaining the zero state. However, in fact, as described above, since a resonance phenomenon occurs between the inductor L1 and the interelectrode capacitance of the switching element SW1, a minute oscillating current flows between the inductor L1 and the switching element SW1.

In this case, this oscillating current may be superimposed on the current IL1 of the inductor L1 when the switching element SW1 is turned on. FIG. 4 is a diagram showing waveforms of the drain-source voltage Vds and the current IL1 of the inductor L1 when the switching element SW1 is turned on near the voltage zero cross of the AC power supply. FIG. 5 is a diagram showing Vds and IL1 when the switching element SW1 is turned on near the voltage peak of the AC power supply. In FIGS. 4 and 5, td indicates the off period of the switching element SW1. From FIGS. 4 and 5, when the switching element SW1 can be turned on near the voltage zero cross of the AC power supply, it is possible to prevent the oscillation current from being superimposed on the current IL1 of the inductor L1. It can be seen that the oscillating current is superimposed on the current IL1 when the In order to avoid a decrease in power factor, switching element SW1 is turned on at the same oscillation current timing in the half cycle of the AC power supply, or desirably switching current is not superimposed on current IL1 of inductor L1 at the timing The element SW1 has to be turned on.

The inter-electrode capacitance of the switching element SW1 depends on the drain-source voltage, and in a general MOSFET, the inter-electrode capacitance decreases as the drain-source voltage increases. Therefore, since the voltage applied between the drain and the source differs according to the phase of the AC power supply, the oscillation period of the oscillating voltage also differs according to the phase. Specifically, the oscillation period is shorter in the vicinity of the power supply voltage peak than in the vicinity of the power supply voltage zero cross.

From this, in order to eliminate the problem that the oscillating current is superimposed on the current IL1 when the switching element SW1 is turned on, it is necessary to change the off period td in accordance with the cycle of the power supply voltage. Even if the off period Td of the switching element SW1 is determined so that the switching element SW1 is turned on near the zero cross of the AC power supply where the oscillating current superimposed on the current IL1 of the inductor L1 shown in FIG. Can not be used for the whole period. That is, since the oscillation period becomes short near the power supply voltage peak, when the off period Td of FIG. 5 and the off period Td of FIG. 4 coincide with each other, the switching element SW1 is turned on near the peak of the oscillation current. is there. In this case, the oscillating current is superimposed on the current IL1 of the inductor L1.

From the above consideration, if the off period Td is a fixed value, it can not be avoided that the oscillating current is superimposed on the current IL1 of the inductor L1. Therefore, in FIG. 2, it is conceivable to detect the first oscillation voltage fall and to turn on the switching element SW1 after a predetermined delay time has elapsed from there. Such an operation sequence is referred to as a comparative example. In the case of the comparative example, it is necessary to set the delay time longer in order to obtain the same switching frequency as in the case of the present embodiment in which the delay time is provided from the time when the second fall of the oscillating voltage is detected. However, when the delay time is also a constant value in the AC power supply half cycle as in the on time of the switching element SW1, the delay time becomes longer, so the delay time becomes susceptible to the fluctuation of the oscillation cycle as described above. That is, since the delay time is long in the comparative example, the oscillating current is likely to be superimposed on the current IL1 of the inductor L1. Therefore, as in the comparative example, when the switching element SW1 is turned on after the first oscillation voltage fall is detected and a predetermined delay time elapses therefrom, the input current waveform is distorted and the power factor is lowered. Do.

However, in the present embodiment, control unit 5 sets a predetermined delay after the elapse of the first off period until the oscillating voltage of detection winding L2 falls at least twice after switching element SW1 is turned off. The off state of the switching element SW2 is continued until the second off period, which is time, elapses. Then, after the second off period has elapsed, the switching element SW1 is turned on. That is, under the condition that the drive frequency at the time of light load increases, the number of falling times of the oscillating voltage is counted as the off period of switching element SW1 necessary to suppress the increase in switching frequency. A period is set which is the sum of the time until reaching the set number of times and the delay time. As a result, the delay time can be shortened, and the influence of the fluctuation of the vibration cycle can be reduced. In other words, since the first off period can be provided long enough by counting the falling of the oscillating voltage twice or more, it is susceptible to the fluctuation of the oscillating cycle, and the ratio of the delay time fixed at the power supply half cycle Can be made smaller. Therefore, speaking quantitatively, it is preferable to make the first off period longer than the second off period.

In addition, when the number of falling of the oscillation voltage is counted and the switching element SW1 is turned on immediately after counting the predetermined number of times, the settable off period depends on the oscillation cycle, so the setting freedom is It is small and can not be set to any frequency. Therefore, as described in the first embodiment, it is necessary to add a second off period, which is a delay time, to the first off period. In addition, since the oscillating voltage is attenuated with the passage of time, a limit value occurs in setting the off period only by the falling count of the oscillating voltage. That is, when the oscillating voltage is attenuated, a trigger signal for turning on the switching element next time can not be obtained. On the other hand, in the method of the first embodiment, the off period of the switching element SW1 can be freely set according to the load.

Next, the calculation load when the control unit 5 is configured by a microcomputer will be considered. When the current IL1 is monitored for each switching of the switching element SW1 and the timing at which the switching element SW1 is turned off is determined so that the peak value has a sine wave, a large calculation load is applied. In this case, it is necessary to use a microcomputer capable of high-speed operation, resulting in high cost. On the other hand, in the light source lighting device according to the first embodiment, the control unit 5 can set the change timing of the on time of the switching element involved in the constant voltage feedback control of the DC voltage to be near the zero cross of the AC power supply. Therefore, the on time of the switching element SW1 may be updated every half cycle of the AC power supply, and this can be made a constant value in the other periods. Further, in a period in which the output of the power factor correction circuit 3 is constant, the control unit 5 can set the second off period to a substantially fixed value. By reducing the processing load as described above, the control unit 5 can be configured by an inexpensive microcomputer having a low calculation processing speed.

Next, the update of the on time of the switching element is considered. In the present embodiment, the control unit 5 sets the on time of the switching element SW1 to a substantially fixed value at least during a half cycle of the AC power supply. That is, in order to improve the power factor, the on time of the switching element SW1 is updated every half cycle of the AC power supply. The purpose is to prevent the on time of the switching element SW1 from largely fluctuating at least during a half cycle of the AC power supply. If the on time of the switching element SW1 does not greatly fluctuate during the half cycle of the AC power supply, the method of updating the on time may be changed. For example, the response speed of feedback control for maintaining the output voltage at a desired voltage may be set to a sufficiently low speed so as not to largely fluctuate between power supply half cycles of the AC power supply. That is, although the on time of the switching element SW1 is changed between the half cycles of the AC power supply, the amount of change is sufficiently reduced. More specifically, the loop gain of feedback control is set to be equal to or less than one-half (0 dB) in one-half or more cycles of the AC power supply 1. In other words, the frequency is set to be less than or equal to one time (0 dB) at a frequency equal to or less than twice the frequency of the AC power supply 1. For example, when the power supply frequency is 50 Hz, constant voltage feedback control is performed by setting the loop gain of constant voltage feedback control to 1 or less (0 dB) or less in that half cycle, that is, 100 Hz or less corresponding to a half wave. Set to not respond in a cycle shorter than 1/2. Thus, the variation of the on-time t (ON) of the switching element SW1 can be suppressed within a half cycle of the power supply cycle, and the same effect can be obtained. Also in this case, since it is not necessary to monitor the current of the inductor L1 and control the peak current for each switching, a microcomputer with a low processing speed can be used.

The number of falling of the oscillating voltage detected in the first off period and the delay time which is the second off period may be variable according to the load or the power supply voltage. Specifically, in the case of driving in the normal current critical mode, the off period of the switching element SW1 can be increased as the driving frequency is increased. For example, as the LED current decreases and the load decreases, at least one of the number of falling of the oscillating voltage detected in the first off period and the delay time that is the second off period is increased. Alternatively, when the power supply voltage is not AC 100 V input but AC 200 V input, at least one of the number of falling of the oscillating voltage detected in the first off period and the delay time as the second off period is increased. These can be easily set by setting conditions for increasing the frequency in advance to a program or the like based on a detection signal from the dimming signal interface 8 or the power supply voltage detection unit 5d. In addition, when the driving frequency is sufficiently low, switching to normal current critical mode control may be performed.

FIG. 6 is a flowchart of processing performed inside the control unit 5 when the control unit 5 is configured by a microcomputer. First, in step S1, the control unit 5 turns on the switching element SW1. When the switching element SW1 is turned on in step S1, the count value of the oscillating voltage signal is reset in step S2, and the count value of the delay time is reset in step S3.

In step S4, it is determined whether the on time of the switching element SW1 has reached a specified value. If the on time has reached the specified value, the switching element SW1 is turned off in step S5. Next, in step S6, counting of the number of falling of the oscillating voltage signal is started. In the first embodiment, the falling of the oscillating voltage is detected twice or more. In step S7, it is determined whether the number of falling times of the oscillating voltage has reached a specified number. If the number of falling times has reached the specified number, counting of delay times is started in step S8. In step S9, it is determined whether the count value of the delay time has reached a specified time. If the delay time has reached a specified time, the process returns to step S1 and the switching element SW1 is turned on again.

As described above, according to the first embodiment of the present invention, in the power factor correction circuit with light load operation, the number of times of oscillation of the oscillating voltage becomes a predetermined number, and thereafter a predetermined delay time elapses. , And maintain the off state of the switching element SW1. Thereby, the rise of the drive frequency can be suppressed while suppressing the harmonics. Further, the timing at which the on-time of the switching element SW1 is updated is set, for example, near the zero cross at every half cycle of the power supply, and is set to a fixed value in the other periods. Therefore, the processing load of the control unit 5 can be significantly reduced.

In the present embodiment, the on time of the switching element SW1 is the same time within a half cycle of the AC power supply, but the switching element SW1 may be driven with the on time of a specific pattern. For example, the power factor correction circuit 3 includes the filter capacitor C1 for the purpose of removing switching ripples. However, when the filter capacitor C1 is provided, the input current is slightly advanced in phase with respect to the power supply voltage, which causes the power factor decrease. . Therefore, in order to correct this, for example, the on time of the switching element SW1 may be temporally changed in the pattern shown in FIG. By driving the switching element with the on time shown in FIG. 7 for a half cycle of the AC power supply, the lead phase can be compensated and the power factor can be improved.

Even when the on-time is transitioned in such a specific pattern, the on-time for feedback control of the output voltage is updated every half cycle of the power supply, for example, near the zero cross, so the processing load on the control unit 5 is significantly reduced. it can. When the on-time is updated, for example, as shown in FIG. 7, the on-time is increased or decreased while maintaining the tendency of the specific pattern.

In addition to the above-described modifications, the light source lighting device 100 and the lighting fixture according to Embodiment 1 of the present invention can be variously modified without losing their features. For example, the control unit 5 may be realized by hardware or software using a microcomputer. At least a part of the control unit 5 may be configured by a microcomputer. FIG. 8 is a block diagram showing the control unit 5 implemented by hardware. In this case, the output voltage detection unit 5a, the power supply voltage detection unit 5d, and the vibration voltage detection unit 5e of FIG. 1 are the receiving device 20 of FIG. The respective functions of the drive unit 5b and the delay time setting unit 5c of FIG. 1 are realized by the processing circuit 22 of FIG. The processing circuit 22 is dedicated hardware. The processing circuit 22 corresponds to, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. Each function of the drive unit 5b and the delay time setting unit 5c may be realized by the processing circuit 22, or the function of each unit may be realized by the processing circuit 22.

FIG. 9 is a block diagram showing the control unit 5 implemented by software. In this case, the output voltage detection unit 5a, the power supply voltage detection unit 5d, and the oscillating voltage detection unit 5e of FIG. 1 are the receiving device 30 of FIG. When the processing circuit is a CPU, each function of the drive unit 5b and the delay time setting unit 5c in FIG. 1 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 34. The processor 32, which is a processing circuit, reads out and executes the program stored in the memory 34 to realize the functions of the respective units. That is, there is a memory 34 for storing a program that results in the operations described in the flowchart of FIG. 6 and the first embodiment. It can be said that this program causes a computer to execute the above procedure or method. Here, the memory corresponds to, for example, non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD. A part of each function of drive unit 5b and delay time setting unit 5c may be realized by dedicated hardware and a part may be realized by software or firmware.

Although an LED is used as the light source 9, another light source may be used. For example, an organic EL (Electro Luminescence) element may be used. The expression "substantially fixed" used in the present embodiment does not mean that a certain value is strictly fixed, but is fixed in design. Therefore, the change of a certain value due to an actual operation error or measurement error is included in the term substantially fixed.

The switching element SW1 may be formed of Si or a wide band gap semiconductor. When the switching element SW1 is formed of a wide band gap semiconductor, the switching frequency can be increased. For example, in the MOSFET made of Si, even if the switching frequency is increased to 300 kHz, the wide band gap can be increased to, for example, 500 kHz. If the upper limit of the switching frequency is high, the upper limit of the frequency to which the current critical mode can be applied can be increased to reduce the load on the microcomputer. The modifications mentioned in the first embodiment can also be applied to a light source lighting device and a lighting apparatus according to the following embodiments. Since the light source lighting device and the lighting apparatus according to the following embodiments have many points in common with the first embodiment, the differences with the first embodiment will be mainly described.

Second Embodiment
The light source lighting device and the lighting apparatus according to the second embodiment differ from the light source lighting device according to the first embodiment in the operation of the control unit 5 during light adjustment in order to cope with a wide load fluctuation.

FIG. 10 is a diagram showing the correspondence between the light source current and the off period of the switching element SW1 according to the second embodiment. As described in the first embodiment, the off period of the switching element SW1 is the sum of the first off period for detecting the falling of the oscillating voltage and the second off period which is a predetermined delay time. When the light source current is gradually decreased from the state where the light source current which is the current of the light source 9 is large, the number of falling of the oscillating voltage detected in the first off period is gradually increased in order to suppress the frequency rise. FIG. 10 shows that as the light source current decreases, the number of falling of the oscillating voltage detected in the first off period increases every two to five times. As the number of falling of the oscillating voltage increases, the off period of the switching element SW1 increases. At this time, the delay time can be made approximately constant.

Next, the case of further reducing the light source current will be described. When the light source current decreases to a predetermined value, and the number of falling times of the oscillating voltage reaches the upper limit number, the further decrease of the light source current corresponds to the increase of the delay time. At this time, when the number of falling of the oscillating voltage reaches the upper limit, the progress of the delay time is prioritized and the oscillating voltage signal is ignored even if the falling of the next oscillating voltage is detected. That is, when the upper limit of the number of falling times set in advance is reached, the counting of the number of falling times is not necessary.

FIG. 11 is an operation waveform in the case where the upper limit number of falling times of the oscillating voltage is set to three and the delay time is set after the number of falling times reaches the upper limit. During a period from time t1 to t2, the current IL1 of the inductor L1 decreases and reaches zero. The number of falling times of the oscillating voltage from the detection winding L2 is counted in a period from time t2 to time t3. From the set light source current value, it is possible to set the upper limit of the number of fallings and the delay time by, for example, referring to a table by a program of a microcomputer constituting the control unit 5 or the like. Here, the number of falling times and the delay time are set three times. The number of falling times of the oscillating voltage of the detection winding L2 reaches three times at time t3. The delay time count starts from time t3 and reaches the delay time set at time t4. The off state of the switching element SW1 is maintained from time t1 to time t4.

During the period from time t3 to t4 during the delay time counting, even if the falling of the oscillating voltage due to the detection winding L2 is detected, the falling voltage is ignored. Even if the oscillating voltage is attenuated during the period from time t3 to time t4, the switching element SW1 is turned on when the set delay time is reached, so there is no problem. Conversely, it is desirable that the upper limit value of the number of falling times be set to the maximum value within the range in which the oscillating voltage can be detected. When the delay time set at time t4 is reached, the switching element SW1 is turned on again, and the next switching cycle is started. As described above, since the period from time t2 to t4 is set according to the light source current, it is possible to suppress an increase in frequency.

As described above, in the second embodiment, the control unit 5 increases the number of falling times of the oscillating voltage detected in the first off period as the load power decreases, thereby lengthening the off period of the switching element SW1. An upper limit is provided for the number of falling of the oscillating voltage detected in the first off period. After increasing the number of falling times of the oscillating voltage detected in the first off period, the control unit 5 lengthens the second off period if the load power is further reduced. By doing this, when the off period of the switching element SW1 has to be extended in the light load state, the off period of the switching element can be sufficiently secured even if the oscillation voltage is attenuated and the falling voltage can not be detected. it can. That is, an increase in switching frequency can be suppressed even in a light load state. Therefore, in the light source lighting device of the second embodiment, the variable width of the light source current is large, the adjustment range of the brightness of the light source can be widely set, and wide load fluctuation can be coped with.

As described in the first embodiment, it is desirable to set the delay time so that the next on-timing comes in the vicinity of the bottom of the oscillation of the voltage between the drain and the source of the switching element SW1. At this time, since the delay time is counted from the latest falling signal of the oscillating voltage, the delay time can be minimized, and the influence of the fluctuation of the oscillating cycle of the oscillating voltage due to the voltage phase of the AC power supply can be reduced. That is, it is possible to minimize the occurrence of distortion in the input current waveform by superimposing the oscillating current on the current IL1 of the inductor L1.

In the present embodiment, the off period of the switching element SW1 is set according to the light source current. However, if the load is light, the frequency rises, so the same control may be performed, for example, when the voltage applied to the light source decreases and the load becomes light. For example, when the light source 9 connected to the DC-DC converter 4 is replaced with one having a low applied voltage, the number of oscillations or the delay time of the oscillating voltage may be increased, or the voltage applied to the light source 9 and the light source The product of the current may be calculated, the load power may be calculated, and the number of oscillations or the delay time of the oscillating voltage may be adjusted according to the load power. In addition, since the drive frequency is increased or decreased depending on the AC power supply voltage, the number of oscillations and the delay time of the oscillation voltage may be adjusted according to the AC power supply voltage. When the drive frequency is a sufficiently low operating condition, the power factor correction circuit 3 may be operated by switching to the normal current critical mode control.

In the second embodiment, the number of falling of the oscillating voltage detected in the first off period is increased as the light source current decreases, and the delay time is increased when the light source current decreases. However, when the light source current is small, the oscillation voltage may not be detected if the first off period is extended. In that case, it is preferable to lengthen the delay time without fixing and increasing the number of falling times of the oscillating voltage detected in the first off period, for example, twice. That is, the control unit 5 lengthens the second off period while fixing the number of falling of the oscillating voltage detected in the first off period as the load power decreases. Thereby, the off period of the switching element SW1 can be extended while solving the problem that the falling of the oscillating voltage can not be detected when the oscillating voltage is small. Furthermore, even if the delay time is increased when the oscillating voltage is small, the current superimposed on the current of the inductor L1 is small, so there is almost no problem.

Third Embodiment
FIG. 12 is a cross-sectional view of the lighting fixture 200 according to the third embodiment. The lighting fixture 200 includes a lighting fixture body 40, a connector 41, a light source substrate 42, and a light source lighting device 43. The lighting device main body 40 is a housing for attaching the light source lighting device 43 and the like. The connector 41 is a connection unit for receiving supply of power from an AC power supply such as a commercial power supply. The light source substrate 42 is a substrate on which a light source such as an LED or an organic EL is mounted.

The circuit configuration of the light source lighting device 43 is the same as that of any of the light source lighting devices described above. Therefore, the lighting fixture 200 of Embodiment 3 is provided with the above-mentioned light source lighting device, and LED or organic EL which the light source lighting device makes it light. The light source lighting device 43 receives power supply from an AC power supply via the connector 41 and the wiring 44. The light source lighting device 43 converts the input power and supplies the converted power to the light source substrate 42 through the wiring 45. The power supplied from the light source lighting device 43 causes the light source mounted on the light source substrate 42 to light.

Thereby, the lighting fixture 200 provided with the advantage of the light source lighting device according to the first or second embodiment is provided. According to this lighting fixture 200, by providing any one of the light source lighting devices described in

Embodiment

1 or 2, it is possible to suppress the increase in switching loss and the light source flicker due to the increase in switching frequency.

3 Power factor correction circuit, 5 control units, 5c delay time setting unit, 9 light sources

Claims

A rectifier circuit that rectifies AC power;
A power factor improvement circuit having a switching element and an inductor, the output of the rectifier circuit being input, and a DC voltage being output;
A detection winding for detecting a voltage generated by the inductor;
A control unit which receives the voltage detected by the detection winding and drives the switching element;
The control unit is configured to perform the switching until a predetermined second off period elapses after a first off period until the oscillating voltage of the detection winding falls at least twice after the switching element is turned off. A light source lighting device characterized by continuing an off state of the element and turning on the switching element after a lapse of the second off period.
The light source lighting device according to claim 1, wherein the control unit sets the on time of the switching element to a substantially fixed value at least during a half cycle of the AC power supply.
The light source lighting device according to claim 1, wherein the control unit sets the second off period to a substantially fixed value during a period in which the output of the power factor correction circuit is constant.
The light source lighting device according to claim 2, wherein the control unit sets a change timing of the on time of the switching element accompanying constant voltage feedback control of the direct current voltage to be near a zero cross of the alternating current power supply.
The light source lighting device according to any one of claims 1 to 4, wherein the control unit increases the number of falling times of the oscillating voltage detected in the first off period as the load power decreases. .
The control unit may increase the second off period if the load power is further reduced after increasing the number of falling times of the oscillating voltage detected in the first off period. The light source lighting device according to Item 5.
5. The controller according to any one of claims 1 to 4, wherein the control unit lengthens the second off period while fixing the number of falling of the oscillating voltage detected in the first off period as the load power decreases. The light source lighting device according to item 1.
The light source lighting device according to any one of claims 1 to 7, wherein at least a part of the control unit is configured by a microcomputer.
The light source lighting device according to any one of claims 1 to 8, wherein the first off period is longer than the second off period.
A light source lighting device according to any one of claims 1 to 9,
A light fixture comprising: an LED for lighting the light source lighting device.
A light source lighting device according to any one of claims 1 to 9,
A light fixture comprising: an organic EL to be lighted by the light source lighting device.