JP2020027752A - Lighting device and lighting apparatus using the same - Google Patents

Abstract

To provide a lighting device in which operation is stabilized by reducing loss, and to provide a lighting apparatus using the same.SOLUTION: A lighting device includes a DC power supply circuit 202, a DC power supply control circuit 204 for controlling the output voltage from the DC power supply circuit 202, a current adjustment circuit 206 for controlling a current flowing to a light-emitting device 210, and a feedback circuit 208 for supplying a feedback signal, according to the voltage at a junction point of the light-emitting device 210 and the current adjustment circuit 206, to the DC power supply control circuit 204. The feedback circuit 208 detects the voltage at the junction point, only when a current is flowing to the current adjustment circuit 206 during PWM dimming control, and supplies the feedback signal to the DC power supply control circuit 204. The DC power supply control circuit 204 controls the output voltage from the DC power supply circuit 202 according to the feedback signal, so that the voltage at the junction point when a current is flowing in the current adjustment circuit 206 is within a predetermined range.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. 12 shows a configuration example of a conventional lighting device 100. In the lighting device 100, the voltage applied from the DC power supply circuit 10 to the light emitting element 12 is adjusted by controlling the switching element Q1 in the current adjusting circuit 14 in accordance with the DC dimming signal and the PWM dimming signal. I do. When the PWM dimming signal is at a high level (H), the switching element Q1 is turned on, and when the PWM dimming signal is at a low level (L), the switching element Q1 is turned off. The duty ratio of the ON state and the OFF state of the switching element Q1 can be changed according to 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 output voltage V _0, 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 is there. 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. On the other hand, the terminal voltage V _D of the current regulating circuit 14 is a value obtained by subtracting the forward voltage V _F of the light-emitting element 12 from the output voltage V ₀ which the DC power source circuit 10, the loss of the DC power supply circuit 10 is the output current I _OUT and the terminal since the product of the voltage V _D, the greater the loss of the DC power supply circuit 10 to have a high output voltage V _0.

Further, when the switching element 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 while reducing a loss of a constant current circuit, 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 with the light emitting element to control a current flowing through the light emitting element according to the dimming command value; and a connection between the light emitting element and the current adjustment circuit. A feedback circuit that detects a voltage at a point and supplies a feedback signal corresponding to the voltage at the connection point to the DC power supply control circuit, wherein the current adjustment circuit supplies a PWM-modulated current to the light emitting element. PWM dimming control is performed, and the feedback circuit performs the connection only when a current flows through the current adjusting circuit when the current adjusting circuit is under PWM dimming control. Detecting a voltage at a point and supplying the feedback signal corresponding to the voltage to the DC power supply control circuit, wherein the DC power supply control circuit responds to the feedback signal when a current flows through the current adjustment circuit. A lighting device, wherein an output voltage of the DC power supply circuit is controlled so that a voltage at the connection point falls within a predetermined range.

  Here, the current adjustment circuit includes a DC dimming control for supplying a constant current to the light emitting element according to the dimming command value, and a PWM dimming control for supplying a PWM modulated current to the light emitting element. , Is preferably switched.

  The feedback circuit is turned on only when a current flows through the current adjustment circuit, and supplies the voltage at the connection point as the feedback signal to the DC power supply control circuit when the current is turned on. It is preferable to include a rectifying element that does not supply the voltage at the connection point as the feedback signal to the DC power supply control circuit when not in the state.

  Further, the feedback circuit uses the voltage at the connection point as a feedback signal after a lapse of a predetermined time during which the high / low level of the voltage at the connection point has been switched in synchronization with the PWM dimming control of the current adjustment circuit as the feedback signal. It is preferable to supply the power to the power supply control circuit.

  Further, the DC power supply control circuit includes a comparison circuit for comparing a constant voltage reference value with the feedback signal, and the DC power supply so that the constant voltage reference value and the value of the feedback signal fall within a predetermined range. It is preferred to control the output voltage of the 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 embodiment is a lighting device including the lighting device.

  Advantageous Effects of Invention According to the present invention, it is possible to provide a lighting device with reduced loss and stable operation, and a lighting fixture using the same.

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 illustrating generation of a feedback signal according to the embodiment of the present invention. FIG. 4 is a diagram illustrating another example of the feedback circuit according to the embodiment of the present invention. FIG. 4 is a diagram illustrating another example of the feedback circuit according to the embodiment of the present invention. FIG. 4 is a diagram for explaining processing in a feedback circuit 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. FIG. 14 is a diagram illustrating a specific circuit configuration of a lighting fixture according to a second modification. FIG. 13 is a diagram for describing processing of a lighting fixture according to a second modification. FIG. 14 is a diagram illustrating a specific circuit configuration of a lighting fixture according to a third modification. FIG. 9 is a diagram illustrating a configuration of a conventional 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. 2, 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. 2, 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. 2, 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.

Feedback circuit 208 outputs a feedback signal FB to the DC power supply control circuit 204 on the basis of the output voltage _{V D} of the current regulating circuit 206. In the present embodiment, as shown in FIG. 2, the feedback circuit 208 includes a bottom hold circuit. The feedback circuit 208 is configured by combining a diode D _FB , a resistor R _FB and a capacitor C _FB .

The feedback circuit 208, 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 input. Output voltage _{V D} is the diode _{D FB} when less than the reference voltage _{V CC} is turned on, a voltage obtained by subtracting the forward voltage of the diode _{D FB} from the output voltage _{V D} is applied to the resistor _{R FB} and the capacitor _{C FB.} Thus, the capacitor C _FB is charged, the lower limit value of the output voltage V _D is held. Here, the resistor R _FB is a discharge resistor, and the time constant CR of the resistor R _FB and the capacitor C _FB is set to a value sufficiently larger than the repetition period of the PWM signal. Reference voltage V _CC is greater than the reference voltage V _REF of the shunt regulator Q _SR of the DC power supply control circuit 204, the switching element Q1 and becomes smaller as a value than the drain voltage when the off-state.

Figure 4 shows the relationship between the feedback voltage _{V R} of the output voltage _{V D} and the feedback circuit 208. As shown in FIG. 4, when the switching element Q1 is in the OFF state is cut off the output voltage V _D, the shunt regulator Q of the output voltage V a bottom voltage of the _D DC power supply control circuit 204 only when the switching element Q1 is turned on Transmit to _SR .

Note that the feedback circuit 208 may be a bottom hold circuit using an operational amplifier as shown in FIG. In the circuit of Figure 5, by using the operational amplifier, as large as the voltage between the output voltage V _D without being affected by the forward voltage of the diode D _FB is output as a feedback voltage V _R. That is, it is possible to eliminate the influence of the forward voltage of the diode D _FB to the output voltage V _D.

The feedback circuit 208, as shown in FIG. 6 may be configured to hold a lower limit value of the output voltage V _D by using a trigger signal synchronized with the PWM signal. As shown in FIG. 7, in the feedback circuit 208, in synchronization with the PWM modulation cycle of the current adjustment circuit 206, a trigger is applied after a predetermined time has elapsed from the timing of switching between the high level and the low level in the PWM modulation, and the capacitor C _FB controlled to retain the lower limit value of the output voltage V _D to. With such a configuration, it is possible to avoid a decrease in responsiveness due to the time constant CR of the resistor R _FB and the capacitor C _FB , and it is possible to improve load following ability.

As described above, in the lighting device 200 and the lighting fixture 300 of the present embodiment, the feedback from the feedback circuit 208 to the feedback signal FB based on the output voltage V _D of the current regulating circuit 206 to the DC power supply control circuit 204, a feedback signal switching control of the switching element _{Q SW} of the DC power supply circuit 202 in accordance with the FB. The output voltage 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 voltage V _R of the feedback signal FB based on the output voltage V _D to control the V _0. Thus, while the output voltage V ₀ which from the DC power supply circuit 202 to be greater than the forward voltage V _F of the light-emitting element 12, the output voltage V ₀ corresponding to the output voltage V _D of the other hand the current regulating circuit 206 This makes it possible to reduce the loss of the lighting device 200 and the lighting fixture 300 as compared with the case where the output voltage V ₀ is always kept constant. Further, it is possible to stably control the terminal voltage V _D of the current regulating circuit 14.

[Modification 1]
FIG. 8 is a diagram illustrating a configuration of the lighting fixture 302 according to the first modification. In the present modified example, the DC power supply circuit 202-1 is configured to include a SEPIC converter that is a non-insulated circuit. The DC power supply control circuit 204, the current adjustment circuit 206, and the feedback circuit 208 may have the same configuration as the lighting fixture 300 of the above embodiment.

Even in such a configuration, the same effect as in the above embodiment can be obtained. Further, since the SEPIC converter is a single-ended converter, the configuration of the DC power supply control circuit 204 for driving the switching element _QSW can be simplified.

[Modification 2]
FIG. 9 is a diagram illustrating a configuration of a lighting fixture 304 according to the second modification. The lighting fixture 304 of this modification has a configuration in which the DC power supply control circuit 204 and the feedback circuit 208 are replaced with a control circuit 212 including a microcomputer. The control circuit 212 includes an analog / digital conversion circuit (A / D conversion circuit). Output voltage V _D of the current regulating circuit 206 is input is converted to a digital signal via an A / D converter to the control circuit 212. The control circuit 212 further receives an input of the PWM signal, sampling the output voltage V _D which is digitally converted in synchronism with the PWM signal. That is, as shown in FIG. 10, in synchronization with the cycle of the PWM modulation of the current regulating circuit 206, when the switching element Q1 is in the OFF state without sampling the output voltage V _D, when the switching element Q1 is in the ON state sampling the output voltage _{V D.} Control circuit 212, the sampled output voltage V _D is greater the duty ratio of the ON state of the greater if the switching element Q _SW than the reference value of the digital values to turn on state of the switching device Q _SW is smaller than the reference value Reduce the duty ratio.

With this configuration, the control circuit 212 including the microcomputer can provide the same effects as those of the above embodiment. Further, it is possible to avoid a decrease in responsiveness due to the time constant CR of the resistor R _FB and the capacitor C _FB , and it is possible to improve load following ability.

[Modification 3]
As shown in FIG. 11, 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 adjustment circuit, 100, 200 lighting device, 202 DC power supply circuit, 204 DC power supply control circuit, 206 current adjustment circuit, 208 feedback circuit, 210 light emitting element, 212 control circuit, 300, 302, 304 Lighting equipment.

Claims (7)

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 feedback circuit that detects a voltage at a connection point between the light emitting element and the current adjustment circuit and supplies a 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;
The feedback circuit detects a voltage at the connection point only when a current flows through the current adjustment circuit when the current adjustment circuit is under PWM dimming control, and outputs the feedback signal corresponding to the voltage. Supply to the DC power control circuit,
The DC power supply control circuit controls an output voltage of the DC power supply circuit such that a voltage at the connection point when a current flows through the current adjustment circuit according to the feedback signal falls within a predetermined range. A lighting device characterized by the above-mentioned. The lighting device according to claim 1,
The current adjustment circuit switches between DC dimming control for supplying a constant current to the light emitting element and PWM dimming control for supplying a PWM modulated current to the light emitting element according to the dimming command value. A lighting device, characterized in that: The lighting device according to claim 1 or 2,
The feedback circuit is turned on only when a current is flowing through the current adjustment circuit, and supplies the voltage at the connection point to the DC power supply control circuit as the feedback signal when the current is turned on. A lighting device comprising a rectifying element that does not sometimes supply the voltage at the connection point to the DC power supply control circuit as the feedback signal. The lighting device according to claim 1 or 2,
The feedback circuit uses the voltage at the connection point as a feedback signal after a lapse of a predetermined time during which the high / low level of the voltage at the connection point has been switched in synchronization with the PWM dimming control of the current adjustment circuit, as the feedback signal. A lighting device, which is supplied to a circuit. The lighting device according to claim 1, wherein:
The DC power supply control circuit includes a comparison circuit that compares a constant voltage reference value with the feedback signal, and controls the DC power supply circuit so that the constant voltage reference value and the value of the feedback signal fall within a predetermined range. A lighting device for controlling an output voltage. The lighting device according to any one of claims 1 to 5,
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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