JP2020027751A - Lighting device and lighting apparatus using the same - Google Patents

Abstract

To provide a lighting device capable of lighting a light-emitting device stably, and to provide a lighting apparatus using the same.SOLUTION: A lighting device includes a feedback circuit 208 for supplying a feedback signal FB according to the output voltage Vfrom a DC power supply circuit 202 to a DC power supply control circuit 204, detecting a voltage Vat the junction point of a light-emitting device 210 and a current adjustment circuit 206, and supplying a feedback signal FB according to the voltage Vto the DC power supply control circuit 204, and controls the output voltage Vfrom the DC power supply circuit 202 to be constant according to the feedback signal FB, when the current adjustment circuit 206 is subjected to PWM dimming control, otherwise controls the output voltage Vfrom the DC power supply circuit 206 so that the voltage Vbecomes constant according to the feedback signal FB.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lighting device and a lighting fixture using the same.

  There is disclosed a technology relating to a lighting fixture that enables the brightness of a light emitting element to be smoothly changed over a wide range (Patent Document 1). In this technology, a first current adjustment unit that adjusts a current flowing through an LED by turning on / off a first transistor in accordance with a PWM signal whose on-duty ratio changes according to an external dimming signal; And a second current adjustment unit that adjusts the current flowing through the LED by changing the voltage applied to the gate of the second transistor according to Then, when the dimming level by the dimming signal is equal to or higher than a predetermined value, the brightness of the LED is controlled by the first current adjusting unit. The brightness of the LED is controlled by the second current adjustment unit while maintaining the control state of the first current adjustment unit in the case of the value.

  In addition, a technique relating to a lighting fixture for suppressing flickering of a light emitting element is disclosed (Patent Document 2). A lighting device according to the related art includes a rectifier circuit, a conversion circuit, a constant current circuit, and a control circuit, and controls an output voltage of an AC / DC conversion circuit so that an output voltage of the constant current circuit becomes constant.

  FIG. 9 shows a configuration example of a conventional lighting device 100. In the lighting device 100, by controlling the transistor Q1 in the current adjustment circuit 14 according to the DC light control signal and the PWM light control signal, the voltage applied from the DC power supply circuit 10 to the light emitting element 12 is adjusted to perform light control. Do. When the PWM dimming signal is at a high level (H), the transistor Q1 is turned on, and when the PWM dimming signal is at a low level (L), the transistor Q1 is turned off. The duty ratio of the ON state and the OFF state of the transistor Q1 can be changed depending on the magnitude of the PWM dimming signal, and accordingly, the brightness of the light emitting element 12 can be adjusted over a wide range.

JP 2015-41430 A JP 2016-100164 A

Meanwhile, when the DC power supply circuit 10 in the conventional lighting apparatus 100 outputs a constant voltage, the output voltage V ₀ is required to be larger than the forward voltage V _F of the light emitting element 12 as a load. However, there are variations in the forward voltage V _F of the light-emitting element 12, and to change with temperature, the output voltage V ₀ which the DC power supply circuit 10 to have a large margin with respect to the forward voltage V _F of the light-emitting element 12 There is a need. Further, when the transistor Q1 is turned off in the PWM dimming state, the forward voltage V _F of the light-emitting element 12 becomes unstable is reduced. In this case, it is desired that can be stably controlled terminal voltage V _D of the current regulating circuit 14.

  An object of the present invention is to provide a lighting device capable of stably lighting a light-emitting element and a lighting fixture using the same.

  One aspect of the present invention is a lighting device that supplies a current based on a dimming command value to a light emitting element, and includes a DC power supply circuit that applies a voltage to the light emitting element, and an output voltage from the DC power supply circuit. A DC power supply control circuit for controlling, a current adjustment circuit connected in series to the light emitting element, for controlling a current flowing through the light emitting element according to the dimming command value, and a current adjusting circuit corresponding to an output voltage of the DC power supply circuit (1) a first feedback circuit that supplies a feedback signal to the DC power supply control circuit, and a voltage at a connection point between the light emitting element and the current adjustment circuit is detected, and a second feedback signal corresponding to the voltage at the connection point is generated. A second feedback circuit for supplying a DC power supply control circuit, wherein the current adjustment circuit is capable of performing PWM dimming control for supplying a PWM-modulated current to the light emitting element. When the current adjustment circuit is under PWM dimming control, the DC power supply control circuit controls the output voltage of the DC power supply circuit to be constant according to the first feedback signal, and the current adjustment circuit performs PWM control. When dimming control is not performed, the DC power supply control circuit controls an output voltage from the DC power supply circuit so that a voltage at the connection point is constant according to the second feedback signal. It is a lighting device.

  Here, it is preferable that a signal having a lower voltage value among the first feedback signal and the second feedback signal is supplied to the DC power supply control circuit.

  Further, the current adjustment circuit is a current adjustment element that controls a current supplied to the light emitting element, a current detection element that detects a current flowing through the current adjustment element, and a current value detected by the current detection element. An error amplification circuit that amplifies a difference from a current command value based on the dimming command value, wherein the current adjustment element detects a detection value detected by the current detection element in accordance with an output of the error amplification circuit. It is preferable to adjust the current supplied to the light emitting element such that the current and the current command value fall within a predetermined range.

  Another embodiment of the present invention is a lighting fixture including the lighting device.

  ADVANTAGE OF THE INVENTION According to this invention, the lighting device which can light a light emitting element stably and the lighting fixture using the same can be provided.

It is a figure showing composition of a lighting device and a lighting fixture in an embodiment of the invention. FIG. 2 is a diagram illustrating a specific circuit configuration of the lighting fixture according to the embodiment of the present invention. FIG. 3 is a diagram illustrating a light control method according to the embodiment of the present invention. FIG. 3 is a diagram for explaining dimming control in the embodiment of the present invention. FIG. 4 is a diagram illustrating another example of dimming control according to the embodiment of the present invention. FIG. 9 is a diagram illustrating a specific circuit configuration of a lighting fixture according to a first modification of the present invention. FIG. 9 is a diagram illustrating light control in a first modification of the present invention. FIG. 9 is a diagram illustrating a specific circuit configuration of a lighting fixture according to a second modification of the present invention. It is a figure showing composition of a conventional lighting device and a lighting fixture.

  The lighting device 200 according to the embodiment of the present invention includes a DC power supply circuit 202, a DC power supply control circuit 204, a current adjustment circuit 206, and a feedback circuit 208. The lighting device 200 is connected to the light emitting element 210. The lighting device 200 and the light emitting element 210 are combined to be used as the lighting fixture 300.

  The DC power supply circuit 202 is a power supply circuit that supplies power to the light emitting element 210. The DC power supply control circuit 204 is a control circuit that controls an output voltage from the DC power supply circuit 202 based on a feedback signal from the feedback circuit 208. The current adjustment circuit 206 is an adjustment circuit that controls the current flowing through the light emitting element 210 based on the dimming signal to adjust the brightness of the light emitting element 210 in light emission. The feedback circuit 208 is a circuit that feeds back the state of the light emitting element 210 and the current adjustment circuit 206 to the DC power supply control circuit 204 as a feedback signal.

  The light emitting element 210 can be, for example, a light emitting diode (LED) or a laser diode (LD). However, the light emitting element 210 is not limited to these, and another light emitting element may be applied. The light emitting element 210 emits light by receiving power from the DC power supply circuit 202. The light emission intensity (brightness) of the light emitting element 210 is controlled by controlling a current value flowing through the light emitting element 210 by the current adjustment circuit 206.

  FIG. 2 is a diagram illustrating a specific circuit configuration of the lighting fixture 300. Hereinafter, the DC power supply circuit 202, the DC power supply control circuit 204, the current adjustment circuit 206, and the feedback circuit 208 will be described with reference to FIG.

The DC power supply circuit 202 has, for example, a configuration including a flyback circuit. The DC power supply circuit 202 includes a rectifier circuit and a switching element Q _SW (power MOSFET or the like). The rectifier circuit is a circuit that receives AC power from a commercial power supply or the like and converts it into DC power. The rectifier circuit can be a full-wave rectifier circuit using a diode bridge. However, the present invention is not limited to this, and the rectifier circuit may include a PFC circuit or an EMI filter circuit. The switching of the switching element _QSW is controlled by the DC power supply control circuit 204. Stored power during ON period isolation transformer of the switching element Q _SW, and outputs the electric power stored by utilizing the counter electromotive force of the isolation transformer by switching off the switching element Q _SW. Thus, it outputs the output voltage V ₀ corresponding to the switching of the switching element Q _SW.

The DC power supply control circuit 204 is a circuit that controls the output voltage V ₀ from the DC power supply circuit 202 by controlling the switching of the switching element _QSW of the DC power supply circuit 202. DC power supply control circuit 204 receives the feedback signal FB from the feedback circuit 208 to be described later, the switching control of the switching element _{Q SW} of the DC power supply circuit 202 according to the feedback signal FB. That is, to control the output voltage V ₀ which from the DC power supply circuit 202 by adjusting the ratio between the on period and the off period of the switching element Q _SW (ON duty ratio) according to the feedback voltage V _R of the feedback signal FB.

In this embodiment, the DC power supply control circuit 204 is a circuit configuration including a shunt regulator Q _SR. Shunt regulator Q _SR has an error amplifier for amplifying the voltage difference between the feedback voltage V _R of the feedback signal FB is input to the reference voltage V _REF and the reference terminal (error voltage), the cathode current corresponding to the error voltage Shed. Cathode current flows in the shunt regulator Q _SR when the feedback voltage V _R exceeds the reference voltage V _REF, the signal is transmitted to the control circuit via photocoupler PC. The control circuit receives the signal from the photocoupler PC, and adjusts the feedback voltage V _R to the reference voltage V _{0 so} that the output voltage V ₀ from the DC power supply circuit 202 increases when the feedback voltage V _R is smaller than the reference voltage V _REF. When the voltage is larger than V _REF , the switching of the switching element _QSW is controlled so that the output voltage V ₀ from the DC power supply circuit 202 becomes smaller.

The current adjustment circuit 206 receives a dimming signal from the outside, and performs control so that the current _IOUT flows to the light emitting element 210 according to the dimming signal. The control circuit of the current adjustment circuit 206 outputs a DC dimming signal and a PWM dimming signal according to the dimming signal from the outside. As shown in FIG. 3, the DC dimming signal is a signal that has a constant value when the dimming signal is less than a predetermined value and monotonically increases when the dimming signal is equal to or more than the predetermined value. As shown in FIG. 3, the PWM dimming signal indicates a duty ratio of the PWM modulation that monotonically increases below the predetermined value, and becomes a constant value above the predetermined value. The DC dimming signal is input to a non-inverting input terminal (+) of an operational amplifier (error amplifier) OP. PWM dimming signal is input to the base terminal of the switching element Q _2. The emitter terminal of the switching element Q ₂ is an operational amplifier the inverting input terminal of the (error amplifier) OP via a resistor R ₂ - is connected to (). Thus, the switching of the switching element Q ₁ is controlled, the dimming signal from the outside is less than the predetermined value current I _OUT to be supplied to the light emitting device 210 is PWM modulated. At this time, the switching of the switching element Q ₁ so as to increase the current I _OUT as the duty ratio indicated by the PWM dimming signal increases is controlled. On the other hand, when the dimming signal from the outside is equal to or more than the predetermined value, the current _IOUT supplied to the light emitting element 210 in response to the DC modulation signal monotonically increases.

In this way, by switching between the DC dimming state and the PWM dimming state, as shown in FIG. 3, when the light emitting element 210 emits light more brightly, the current I _OUT is always supplied to the light emitting element 210, When the light emitting element 210 emits dark light, the PWM modulated intermittent current _IOUT is supplied to the light emitting element 210. Thus, the brightness of the light emitting element 210 can be adjusted in a darker state than in the case where only the DC dimming state is used, that is, in a so-called deep dimming state.

The feedback circuit 208 outputs a feedback signal FB based on either the output voltage V ₀ of the DC power supply circuit 202 or the output voltage V _D of the current adjustment circuit 206 to the DC power supply control circuit 204. In the present embodiment, as shown in FIG. 2, it is configured to include a switching circuit that controls the switching elements SW1 and SW2.

Specifically, when the current adjustment circuit 206 is under PWM dimming control, the switching circuit turns SW1 off and SW2 on. Accordingly, the first feedback signal FB1 corresponding output voltage V ₀ to voltages V ₁ obtained by dividing the DC power supply control circuit 204 is supplied to the DC power supply control circuit 204. On the other hand, when the current adjustment circuit 206 is not under PWM dimming control, the switching circuit turns on SW1 and turns off SW2. Thus, the output voltage V _D is a terminal voltage of the switching element Q1 and the detection resistor R ₀ of the current regulating circuit 206 is supplied to the DC power supply control circuit 204 as the second feedback signal FB2.

DC power supply control circuit 204, when the current regulating circuit 206 is controlled PWM dimming in response to the first feedback signal FB1, DC as the first feedback signal FB1 is equal to the reference voltage _{V REF} of the shunt regulator _{Q SR} The output voltage V ₀ of the power supply circuit 202 is controlled. Thus, the output voltage V ₀ which the DC power supply circuit 202 is controlled to be constant. Further, the DC power supply control circuit 204, when the current regulating circuit 206 is not controlled PWM dimming in response to the second feedback signal FB2, so that the second feedback signal FB2 is equal to the reference voltage _{V REF} of the shunt regulator _{Q SR} To control the output voltage V ₀ of the DC power supply circuit 202. As a result, the output voltage V ₀ from the DC power supply circuit 202 is controlled so that the output voltage V _D of the current adjustment circuit 206 becomes constant.

As shown in FIG. 4, also increases the output voltage V _D switching element Q1 is in the off state when the PWM dimming control is performed, the output voltage V according to the output voltage V ₀ which DC power supply control circuit 204 _The DC power supply circuit 202 is controlled so that ₀ becomes constant. In this case, although the output voltage V _D which may become large, so at the time of PWM dimming control current I _OUT is small, resulting in the loss of the current regulating circuit 206 does not significantly increase. On the other hand, as shown in FIG. 4, when the PWM dimming control is not performed (when the DC dimming control is performed), the output voltage V _D according to the output voltage V _D of the current adjustment circuit 206 is output. Is controlled so as to be constant. Therefore, even if the current I _OUT is larger than that during the PWM dimming control, the loss of the current adjustment circuit 206 can be suppressed.

As shown in FIG. 5, the dimming control value may be divided into three areas smaller than A0, A0 or more, A1 or less, and more than A1, and control may be performed. When dimming command value is less than A0 controls to input the first feedback signal FB1 corresponding to a voltage which is an output voltage V ₀ which DC power supply control circuit 204 divide the DC power supply control circuit 204. When the dimming command value exceeds A1 controls by inputting the DC power supply control circuit 204 the output voltage V _D of the current regulating circuit 206 as the second feedback signal FB2. When the dimming command value is equal to or more than A0 and equal to or less than A1, the first feedback signal FB1 and the second feedback signal FB2 are mixed according to the ratio and input to the DC power supply control circuit 204 for control. By performing such control, as shown in FIG. 5, voltage jump in a switching region between PWM dimming control and DC dimming control (region where the dimming command value is A0 or more and A1 or less) is eliminated. Therefore, when the light emission of the light emitting element 210 is faded in or out, the brightness of the light emitting element 210 can be smoothly controlled without abrupt change.

[Modification 1]
FIG. 6 is a diagram illustrating a configuration of a lighting fixture 302 according to the first modification. In this modification, the feedback circuit 208 in the above embodiment is replaced with a feedback circuit 208-1 having another configuration. The DC power supply circuit 202, the DC power supply control circuit 204, and the current adjustment circuit 206 may have the same configuration as the lighting fixture 300 of the above embodiment.

Feedback circuit 208-1 is configured to include an operational amplifier _Q A, a _{Q B.} The non-inverting input terminal of the operational amplifier Q _A (+) is input the output voltage V _D of the current regulating circuit 206, the inverting input terminal of the operational amplifier Q _A - signal output terminal through the diode is feedback input to the () You. The non-inverting input terminal of the operational amplifier _{Q B} (+) voltages _{V 1} to the output voltage _{V 0} by dividing by the resistance _{R h} and resistances _{R l} of the DC power supply circuit 202 is input, an inverting input terminal of the operational amplifier _{Q B} (- In), the signal of the output terminal is fed back via a diode.

FIG. 7 is a diagram illustrating the operation of the lighting fixture 302 according to the first modification. Dividing ratio of the voltage _{V 0} is set to be DC shunt regulator _{Q SR} of the power supply control circuit 204 reference voltage _{V REF} with respect to _{V REF = V th × R l} / (R h + R l). Here, the voltage threshold V _th, it is preferable to set the voltage larger than the forward voltage V _F of the light emitting element 210 when the switching point C of the DC dimming control and PWM dimming control.

In region A, voltages _{V 1} is higher than the output voltage _{V D.} Then, the diode associated with the operational amplifier Q _B is turned off, the diode associated with the operational amplifier Q _A is turned on. Therefore, the reference terminal of the shunt regulator Q _SR of the DC power supply control circuit 204 output voltage V _D is input. On the other hand, in the region B, voltages _{V 1} is lower than the output voltage _{V D.} Then, the diode associated with the operational amplifier Q _B is turned on, the diode associated with the operational amplifier Q _A is turned off. Therefore, the voltages _{V 1} is input to the reference terminal of the shunt regulator _{Q SR} of the DC power supply control circuit 204.

With such a configuration, the output voltage V ₀ which from the DC power supply circuit 202 so that the output voltage V _D on the basis of the output voltage V _D in the area A is maintained constant is controlled. Further, the output voltage V ₀ which from the DC power supply circuit 202 so that the voltages V ₁ is maintained constant based on the voltages V ₁ in the region B is controlled.

  As described above, even with the configuration of the lighting fixture 302 in the first modification, the same effects as those of the lighting fixture 300 in the above embodiment can be obtained.

[Modification 2]
As shown in FIG. 8, a configuration may be employed in which a smoothing capacitor C is connected between the output terminals of the current adjustment circuit 206. As a result, the current that is turned on / off by the current adjustment circuit 206 is rectified, so that it is possible to suppress flickering of light, a feeling of afterimage in the light emitting element 210, generation of flicker at the time of shooting, and the like.

  Note that, instead of the smoothing capacitor C, a configuration in which a filter circuit capable of smoothing a current may be provided.

Reference Signs List 10 DC power supply circuit, 12 light emitting element, 14 current adjusting circuit, 100, 200 lighting device, 202 DC power supply circuit, 204 DC power control circuit, 206 current adjusting circuit, 208 feedback circuit, 210 light emitting element, 300, 302 lighting equipment.

Claims (4)

A lighting device that supplies a current based on a dimming command value to a light emitting element,
A DC power supply circuit for applying a voltage to the light emitting element;
A DC power supply control circuit for controlling an output voltage from the DC power supply circuit,
A current adjustment circuit connected in series to the light emitting element and controlling a current flowing through the light emitting element according to the dimming command value;
A first feedback circuit that supplies a first feedback signal corresponding to an output voltage of the DC power supply circuit to the DC power supply control circuit;
A second feedback circuit that detects a voltage at a connection point between the light emitting element and the current adjustment circuit and supplies a second feedback signal corresponding to the voltage at the connection point to the DC power supply control circuit;
With
The current adjustment circuit is capable of performing PWM dimming control for supplying a PWM-modulated current to the light emitting element;
When the current adjustment circuit is under PWM dimming control, the DC power supply control circuit controls the output voltage of the DC power supply circuit to be constant according to the first feedback signal, and the current adjustment circuit When PWM dimming control is not performed, the DC power supply control circuit controls an output voltage from the DC power supply circuit so that a voltage at the connection point is constant according to the second feedback signal. Lighting device. The lighting device according to claim 1,
A lighting device, wherein a signal having a lower voltage value among the first feedback signal and the second feedback signal is supplied to the DC power supply control circuit. The lighting device according to claim 1 or 2,
The current adjustment circuit,
A current adjusting element for controlling a current supplied to the light emitting element;
A current detection element for detecting a current flowing through the current adjustment element;
An error amplifier circuit that amplifies a difference between the current value detected by the current detection element and a current command value based on the dimming command value,
With
The current adjustment element adjusts a current supplied to the light emitting element such that a detection value detected by the current detection element and the current command value fall within a predetermined range according to an output of the error amplification circuit. A lighting device characterized by adjusting. A lighting fixture comprising the lighting device according to claim 1.

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