JP2019212535A - Light source lighting device and lighting fixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a visual change in brightness which is seen stepwise when an output current is changed according to a change in a PWM signal in a light source lighting device in which a control circuit such as a microcomputer controls the output current. SOLUTION: Current generators 4 and 5 generate an output current for lighting a light source 12. The control circuit 10 controls the current generators 4 and 5 according to the PWM signal input from the outside to change the output current stepwise discontinuously. The control circuit 10 gradually changes the current value of the output current in two or more steps when changing the output current from the current current value to the next current value in response to the one-step change of the PWM signal. [Selection diagram] Figure 1

Description

  The present invention relates to a light source lighting device and a lighting fixture that control an output current with a control circuit such as a microcomputer.

  There is known a light source lighting device capable of dimming by inputting a PWM signal (see, for example, Patent Document 1). A light source lighting device that controls an output current with a microcontroller or a microcomputer is also known.

Japanese Patent No. 3829286

  The output of the microcomputer is a digital output. Therefore, in the light source lighting device in which the output current is controlled by the microcomputer, the output current cannot be continuously changed even if the light is continuously adjusted by the PWM signal. End up.

  The output current can be continuously changed by adding a circuit for converting the digital output of the microcomputer to analog or a circuit for providing a delay time. However, since a circuit is added, there is a problem that the light source lighting device is increased in size and cost.

  The output current of the light source lighting device is proportional to the brightness of the light source. When the output current changes stepwise during dimming, the brightness also changes stepwise. Therefore, there is a problem that the visual appearance is not good. In particular, when the dimming is performed with a small output current, the rate of change of the output current becomes large even with the same current value change, the change in brightness is felt greatly, and the visual appearance becomes noticeable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to change an output current according to a change in a PWM signal in a light source lighting device that controls an output current by a control circuit such as a microcomputer. It is to reduce the change in visual brightness that appears step by step.

  A light source lighting device according to the present invention includes: a current generation unit that generates an output current for lighting a light source; and the current generation unit is controlled in accordance with a PWM signal input from outside to discontinuously discontinue the output current. The control circuit changes the current value of the output current in two or more stages when the output current is changed from the current current value to the next current value according to the change of the PWM signal. It is characterized by changing it step by step.

  In the present invention, the control circuit changes the current value of the output current stepwise in two or more steps when changing the output current from the current value to the next current value in accordance with the change in the PWM signal in one step. . As a result, in the light source lighting device that controls the output current by a control circuit such as a microcomputer, it is possible to reduce the change in visual brightness that appears stepwise when the output current is changed according to the change in the PWM signal. it can.

It is a figure which shows the lighting fixture in embodiment. It is a figure which shows the conventional light control curve. It is a figure which shows the light control curve of embodiment. It is a figure at the time of changing the conventional dimming degree from 5% to 6%. It is a figure at the time of changing dimming degree from 5% to 6% in embodiment. It is a figure at the time of changing light control degree from 5% to 6% ideally. It is a figure at the time of changing the conventional dimming degree from 5% to 8%. It is a figure at the time of changing dimming degree from 5% to 8% in embodiment. It is a figure at the time of changing light control degree from 5% to 8% ideally.

  FIG. 1 is a diagram illustrating a lighting apparatus according to an embodiment. The lighting fixture includes a power source 1, a light source 12, a PWM dimmer 13, and a light source lighting device 200. The light source lighting device 200 is a device that turns on the light source 12 by receiving an AC voltage from the power source 1 and receiving power. The light source lighting device 200 receives a PWM signal from the PWM dimmer 13 and performs dimming according to the ON-Duty of the PWM signal. In FIG. 1, components other than the power source 1, the light source 12, and the PWM dimmer 13 are components of the light source lighting device 200. The power source 1 may be a DC voltage.

  The light source 12 is, for example, an LED module in which a plurality of LEDs are connected. The light source 12 is not limited to an LED, and any light source can be used as long as it can be turned on by passing a current from the light source lighting device 200. Depending on the type of the light source 12, a circuit configuration suitable for lighting the light source 12 including the rectifier circuit 2 and the smoothing capacitor 3 is used instead of the step-down chopper circuit 100.

  The light source lighting device 200 includes a rectifier circuit 2, a smoothing capacitor 3, a step-down chopper circuit 100, a control circuit 10, a dimming I / F (interface) circuit 11, and connectors 50a to 50f. The step-down chopper circuit 100 includes a switching element 4, a drive circuit 5, a free wheel diode 6, an inductor 7, a capacitor 8, and a current detection resistor 9. The connectors 50 a and 50 b of the light source lighting device 200 are provided for connection with the power source 1, the connectors 50 c and 50 d are provided for connection with the light source 12, and the connectors 50 e and 50 f are for connection with the PWM dimmer 13. Is provided.

  The rectifier circuit 2 performs full-wave rectification on the AC voltage supplied from the power source 1. The rectifier circuit 2 is constituted by a diode bridge, for example. The smoothing capacitor 3 smoothes the pulsating voltage that has been full-wave rectified by the rectifier circuit 2. The rectifier circuit 2 of the present embodiment is a capacitor input rectifier circuit, but is not limited thereto, and any circuit configuration that generates a DC voltage in the smoothing capacitor 3 may be used. For example, when power factor improvement is performed, a boost chopper circuit may be inserted as a power factor correction circuit between the rectifier circuit 2 and the smoothing capacitor 3. The DC voltage smoothed by the smoothing capacitor 3 is supplied to the step-down chopper circuit 100.

  In the step-down chopper circuit 100, as an example, a current detection resistor 9 is provided in series with the light source 12 in order to detect the current of the light source 12. A connection point between the current detection resistor 9 and the light source 12 is connected to the control circuit 10. Since the same current as the light source 12 flows through the current detection resistor 9, the current of the power source 12 can be known from the voltage generated in the current detection resistor 9. The control circuit 10 feedback-controls the voltage of the current detection resistor 9 and controls the current flowing through the light source 12. Here, the switching element 4 is a MOSFET. The drive circuit 5 supplies a gate signal for on / off control of the switching element 4 to the gate of the switching element 4 in accordance with the control signal input from the control circuit 10. The on / off controlled current is stepped down by the inductor 7, smoothed by the capacitor 8, and flows to the light source 12 to turn on the light source 12. The free-wheeling diode 6 becomes a current path for the inductor 7 when the switching element 4 is turned off. Here, the step-down chopper circuit 100 is used as means for supplying current to the light source 12, but means for supplying current to the light source 12 may be other circuits.

  The control circuit 10 supplies a control signal to the drive circuit 5 based on the voltage of the current detection resistor 9 and the voltage of the dimming I / F circuit 11. For example, the control circuit 10 is a microcomputer that can execute a desired operation using a program. Details of the control of the control circuit 10 will be described later.

  The control signal of the switching element 4 output from the control circuit 10 is input to the gate of the switching element 4. In the present embodiment, since the switching element 4 is provided on the high voltage side, a drive signal is electrically transmitted from the drive circuit 5 to the gate of the switching element 4. As the drive circuit 5, a transformer or a photocoupler is generally used. The drive signal is a rectangular wave, and the drive circuit 5 changes the on-duty ratio or frequency of the rectangular wave based on the control signal input from the control circuit 10. The switching element 4 is turned on / off according to the on-duty ratio. As the on-duty ratio increases, the current flowing through the light source 12 increases. As the on-duty ratio decreases, the current flowing through the light source 12 decreases. As described above, the switching element 4 and the drive circuit 5 generate an output current that turns on the light source 12 in accordance with the control signal from the control circuit 10.

  The dimming I / F circuit 11 shapes the waveform of the PWM signal and inputs a voltage to the control circuit 10. The PWM dimmer 13 and the light source lighting device 200 are different products. Since both circuit grounds are different, a direct connection may cause a failure or malfunction. Therefore, it is necessary to insulate from the PWM dimmer 13 with a photocoupler or the like in the dimming I / F circuit 11. Basically, the PWM signal input from the PWM dimmer 13 is insulated by a photocoupler or the like, and the waveform is shaped so as to be the same as the waveform input from the PWM dimmer 13 and input to the control circuit 10. . The control circuit 10 controls the drive circuit 5 and the switching element 4 in accordance with the ON-Duty of the PWM signal to change the output current in a stepwise manner.

  The PWM dimmer 13 is a dimmer for illumination. The PWM dimmer 13 is not limited to a dimmer and may be any one that outputs a PWM signal, and may be a human sensor or the like. The PWM signal output from the PWM dimmer 13 is pulse width modulation, and is controlled by changing the ON-Duty (duty cycle ratio) of the pulse width with a constant period.

  The ON-Duty of the PWM signal will be described. The PWM signal whose waveform is shaped by the dimming I / F circuit 11 performs a switching operation of the semiconductor element when the waveform is shaped. For this reason, even if there is no change in the ON-Duty of the PWM signal output from the PWM dimmer 13, the ON-Duty of the waveform-shaped PWM signal input to the control circuit 10 is always slightly small. It has fluctuated. The amount of fluctuation varies depending on the thing, but is about ± 0.2%.

  The above is presumed that there was no change in the ON-Duty of the PWM signal output from the PWM dimmer 13. However, since the PWM signal is also outputted by performing a switching operation of the semiconductor element, the PWM dimmer 13 always fluctuates slightly even if it outputs a constant signal. The amount of fluctuation varies depending on the thing, but is about ± 0.2%.

  Since the PWM signal always fluctuates slightly, fine control cannot be performed on the ON-Duty of the PWM signal. For example, when the ON-Duty is to be controlled in units of 0.1%, the PWM signal of the PWM dimmer 13 is input to the control circuit 10 via the dimming I / F circuit 11 even if it has not changed. The PWM signal changes slightly. The amount of fluctuation varies depending on the thing, but is about ± 0.2%. For this reason, although the brightness is not changed, the brightness always changes, and in some cases, it looks flickering.

  In order to prevent flicker and the like from occurring, it is desirable to perform control by ON-Duty of the PWM signal in units of 1%. This means that the minimum change width of the brightness change is 1% of ON-Duty. For example, 95% (= 100% -5%) of brightness change from total light (100%) to 5% dimming, and ON-Duty is changed with 0% to 100% change width of 100%. In this case, it is necessary to change the brightness (dimming degree) by about 1% with respect to the change of 1% of ON-Duty.

  A conventional dimming curve and operation will be described. FIG. 2 is an enlarged view of a conventional dimming curve near the lower limit dimming. The horizontal axis represents the PWM signal ON-Duty [%], and the vertical axis represents the dimming degree [%]. As described above, every time the PWM signal changes by 1%, the dimming degree [%] changes by 1% so that flickering does not occur. Since the dimming degree changes from the total light to the lower limit dimming in proportion to the PWM signal, the dimming degree (output current) that changes with respect to the PWM signal ON-Duty 1% at any point is It becomes the same value. The change of the dimming degree when the PWM signal ON-Duty is changed by 1% is a constant value A.

  For example, when the PWM dimming signal ON-Duty is 5%, it lights with all light (100%), and when the ON-Duty is 90%, it lights with 5% output, the output current per 1% ON-Duty Will change by 1.12%. In FIG. 2 and FIG. 3, for the sake of easy understanding, the output current is illustrated as changing by 1% per 1% of ON-Duty.

  Here, a conventional problem will be described in the case of a light source lighting device capable of dimming the output current to 15 mA of 5% dimming with all light of 300 mA. Since the output current changes linearly from all light to 5% dimming according to the PWM dimming signal, the output current per 1% ON-Duty is 3 mA in all cases from all light to 5% dimming. It changes 1% of light 300mA.

  When the output current of ON-Duty 1% is reduced from 300 mA of all light, 3 mA corresponding to ON-Duty 1% is reduced to 297 mA. As described above, since the output current is proportional to the brightness of the light source, the brightness is also reduced by 1%. That is, (297 mA / 300 mA) × 100 = 99%.

  When the output current of ON-Duty 1% is increased from 15 mA of 5% dimming, 3 mA corresponding to ON-Duty 1% increases to 18 mA. Since the output current is proportional to the brightness of the light source, the brightness is increased by 20%. That is, (18 mA / 15 mA) × 100 = 120%.

  Thus, even when the same ON-Duty 1% changes, it can be seen that the smaller the original output current is, the larger the rate of change of the output current (brightness) is. As a result, when the ON-Duty is changed by 1% at the lower limit of dimming, such as 5% dimming, the brightness suddenly changes greatly, and the visual appearance is not good. Some claims may be made.

  FIG. 3 is a diagram illustrating a dimming curve according to the embodiment. A different point from FIG. 2 is demonstrated. In FIG. 2, the change in the dimming degree when the ON-Duty of the PWM signal is changed by 1% is A. In FIG. 3, A is divided into three parts a, b, and c. As explained earlier, it is difficult to change the dimming degree in units of 1% or less in terms of flickering. Therefore, when changing the dimming degree, the dimming degree, that is, the output current is not changed by one change, but the output current is changed in several divisions. Thereby, the change of the output current (brightness) per one time becomes small, and the visual appearance is also improved. Here, it is divided into three, and when changing the dimming degree A, it changes in order of a → b → c or c → b → a and changes A.

  For example, when the output current changes by 3 mA with a change of 1% of ON-Duty, A becomes 3 mA. In FIG. 2, the output current changed by 3 mA with a change of 1% of ON-Duty. On the other hand, in FIG. 3, the output current changes three times by 1 mA with a change of 1% of ON-Duty, and the total changes by 3 mA.

  As a supplement, since the dimming level changes in units of ON-Duty 1%, the dimming level in the middle of a, b, and c is not always lit. It is only used as a point at which the dimming level transitions when the dimming level changes A. Here, although it changed into 3 times for description, the change should just be 2 times or more. As the number of divisions increases, the change per time can be reduced, and the visual appearance is also improved.

  The difference between the two when the dimming signal is actually varied will be described with reference to FIGS. FIG. 4 is a diagram when the dimming degree is changed from 5% to 6% in the prior art. The vertical axis represents dimming degree [%], and the horizontal axis represents time t. The dimming degree is changed by one step from 5% to 6%. FIG. 5 is a diagram when the dimming degree is changed from 5% to 6% in the embodiment. The dimming degree changes from 5% to 6% by repeating small changes such as a, b, and c.

  FIG. 6 is a diagram when the dimming degree is ideally changed from 5% to 6%. In this way, it is desirable to change the dimming degree continuously. By changing continuously, the visual discomfort is much less than when changing step by step. In short, even if it changes stepwise, the more the number of divisions, the more it seems to change continuously and the closer it is to the ideal state. If the control circuit 10 is of a digital control such as a microcomputer, it is difficult to continuously change the dimming degree. However, if the control IC is an analog IC, the dimming degree can be changed continuously. However, in recent years, since the light source lighting device is required to have complicated control such as initial illuminance correction, many of them are equipped with a microcomputer.

  FIG. 7 is a diagram when the dimming degree is changed in three steps from 5% to 8% in the prior art. FIG. 8 is a diagram when the dimming degree is changed in three steps from 5% to 8% in the embodiment. FIG. 9 is a diagram when the dimming degree is ideally changed in three steps from 5% to 8%. Basically, FIG. 7 repeats FIG. 4, FIG. 8 repeats FIG. 5, and FIG. 9 repeats FIG.

  As described above, in the present embodiment, the control circuit 10 changes the current value of the output current when changing the output current from the current value to the next current value in accordance with a one-step change in the PWM signal. Change in two steps or more. As a result, in the light source lighting device that controls the output current by the control circuit 10 such as a microcomputer, the visual brightness change that appears stepwise is reduced when the output current is changed according to the change of the PWM signal. be able to.

  The control circuit 10 is a microcomputer or the like, and controls by dividing a change in dimming degree (output current, brightness) by a written program. The dimming degree is changed stepwise only when the dimming degree is low. For example, in the region where the dimming degree is 50% or more, the number of dimming steps may be reduced stepwise or multiple times. It is not necessary to divide and change the dimming degree. Depending on the way of programming, there is a possibility that the capacity of the program can be reduced by limiting.

4 switching element (current generation unit), 5 drive circuit (current generation unit), 10 control circuit, 12 light source

Claims (2)

A current generator for generating an output current for turning on the light source;
A control circuit that controls the current generator according to a PWM signal input from the outside and changes the output current in a stepwise manner;
The control circuit changes the current value of the output current stepwise in two or more steps when the output current is changed from the current current value to the next current value in accordance with the change of the PWM signal in one step. A light source lighting device characterized by that.   A light fixture comprising the light source lighting device according to claim 1.

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