JP2019061783A - LED lighting device - Google Patents

Abstract

To solve such a problem that, in conventional constant current control, a value of current flowing through an LED is detected to perform feedback control, so that, when a lighting operation is performed, the voltage across an LED is increased from a state where a value of current flowing through the LED is zero until the value of current is increased to a preset current value, but, if responsiveness is poor, the value of current overruns a desired current value, so that an LED lights bright although in a moment (Figure 3 B) and thereafter emits light at a normal light intensity (Figure 3 A), and accordingly there is the case where the brightness at a moment is an eyesore.SOLUTION: In an LED lighting device, at the time when a lighting operation is performed, a weak current the degree of which cannot allow the naked eye to recognize that an LED emits light is flown through an LED (Figure 3 C), and, when the lighting operation is performed, a value of current flowing through an LED is increased from a value of the weak current to a preset current value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an LED lighting device that performs constant current control to adjust a voltage applied to the LED so that the current value flowing to the LED becomes a preset current value when the lighting operation is performed by a lighting on / off switch or the like. .

  The luminous intensity, or brightness, of the LED is approximately proportional to the current flowing through the LED. Therefore, in order to set the luminous intensity at the time of lighting of the LED, it is necessary to set in advance the current flowing through the LED. A resistor for current limiting may be connected to the LED in order to simply set the continuous flow value flowing to the LED, but when it is desired to set the light intensity accurately or aging of the characteristics of the LED occurs Even if the light intensity is desired to be kept constant, constant current control is performed. The constant current control is a method of controlling the current value flowing to the LED to a preset current value by detecting the current value flowing to the LED and feedback controlling the voltage value applied to both ends of the LED. (See, for example, Patent Document 1).

JP 2013-25927 A (paragraph [0019], FIG. 1)

  In the conventional constant current control described above, feedback control is performed by detecting the current value flowing to the LED, so when the lighting operation is performed, the current value flowing to the LED becomes a preset current value from the state of zero current value Increase the voltage across the LED. Therefore, since no current flows in the LED at the time of lighting operation, the constant current control unit causes the voltage to rise sharply, and the value of the current flowing to the LED also rises rapidly in conjunction. Since it is constant current control, it is sufficient to stop the rise of the voltage at both ends when the rapidly rising current value reaches a preset current value and maintain the voltage at that time, but the response in the constant voltage control unit Due to the delay caused by the gender, a state occurs in which the voltage does not stop rising and continues to rise. When the voltage continues to rise, the current value flowing to the LED exceeds the preset current value, so the constant current control unit performs control to lower the voltage applied to the LED, and the current value flowing to the LED is a preset current value. As it settles down, the LED continues to glow at the set light intensity.

  Because of this behavior, immediately after the lighting operation, the light will be brighter than the specified light intensity, though for a moment, and then the light intensity will settle at the set light intensity. There may be a case in which a momentary bright state immediately after the lighting operation is anxious, and it is desirable to eliminate the state.

  Then, this invention makes it a subject to provide the LED lighting device which does not generate | occur | produce a too bright state immediately after lighting operation in view of said problem.

  In order to solve the above problems, the LED lighting device according to the present invention is an LED lighting device that applies a DC voltage to the LED to cause the LED to emit light at a predetermined light intensity when the lighting operation is performed, and a voltage applied to the LED The constant voltage control unit controls the current value flowing to the LED by varying the current value, and the constant voltage control unit sets in advance the current value for the LED to emit light at a predetermined light intensity, and the lighting operation is performed. The constant voltage control unit controls the constant current so that the current flowing through the LED has a preset current value. The constant current control unit controls the lighting operation when the lighting operation is performed. A small amount of current that can not be recognized as being emitted is sent to the LED, and when the lighting operation is performed, the current value flowing to the LED is increased from the weak current value to the preset current value And characterized in that.

  Constant current control after the lighting operation is performed by supplying a weak current to the extent that the light is not recognized by the naked eye to the LED in the state before the lighting operation, that is, the state recognized as the light-off state No feedback is given that the current value is zero.

  By the way, the voltage applied to both ends of the LED may be changed due to aging or the like in order to supply a weak current to the LED, and even if the voltage value is constant and not corrected, even if the voltage is applied to the LED There is a possibility that the current does not flow. Therefore, it is desirable that the constant current control unit corrects the voltage applied to both ends of the LED at the time of the light-off operation in the state where the weak current flows.

  When the lighting operation is performed, if the current continues to flow, although it is weak, wasteful power is consumed. When it is desired to eliminate the unnecessary consumption of power, the constant current control unit cuts off the current to the LED when the lighting operation is not performed within a predetermined time while the weak current is flowing to the LED. At the same time, when the lighting operation is performed while the current to the LED is cut off, constant current control is performed so that the weak current flows to the LED, and then the current value of the LED is increased to the preset current value. Just do it.

  As is apparent from the above description, the present invention prevents generation of the phenomenon in which the LED is illuminated for a moment at a brightness higher than the specified light intensity immediately after the lighting operation by supplying a weak current to the LED at the lighting operation time point can do.

Block diagram showing the configuration of the lighting device of the present invention Diagram showing the relationship between the voltage across the LED and the current value Flow chart showing control contents in constant current control unit Flow chart showing control when lighting operation is performed in the state of current interruption to LED

  Referring to FIG. 1, reference numeral 1 denotes a direct current power source, which is a power source for causing the LED 2 to emit light. When the on / off switch 6 is switched from the off state to the on state, the microcomputer 5 detects the lighting operation and turns on the transistor 51 periodically by a pulse signal by PWM control. Then, a voltage derived from the DC power supply 1 is applied to both ends of the LED 2, a current flows in the LED 2, and the LED 2 emits light.

  The luminous intensity which is the brightness of the LED 2 is approximately proportional to the current flowing to the LED 2. Therefore, by connecting the resistor 3 in series to the LED 2 and loading the voltage at the voltage dividing point m into the microcomputer 5, the microcomputer 5 can detect the current value flowing to the LED 2. In order to keep the light intensity of the LED 2 constant, the microcomputer 5 performs constant current control by adjusting the duty ratio of the on time of the transistor 51 so that the current flowing through the LED 2 becomes a preset value. The microcomputer 5 and the transistor 51 constitute a constant current control unit 4.

  Referring to FIG. 2, when the forward voltage applied to both ends of LED 2 is gradually increased from the zero state, almost no forward current flows until the forward voltage (or lighting voltage) Vf is exceeded. Therefore, the LED 2 does not emit light. When the voltage at both ends exceeds Vf, current starts to flow to the LED 2 and the LED 2 starts to emit light accordingly.

  In the case of conventional constant voltage control, when the target light emission state is A, constant current control is performed so that the current is Ia, but the current is zero at the start of lighting, so the voltage across LED 2 is Increase to Vb beyond Va due to delay of responsiveness. In this B state, since the current is Ib, the light intensity of the B state is larger than that of the A state, that is, light is emitted brighter than expected brightness. However, in the constant current control, since the current value flowing to the LED 2 is held at Ia, the state immediately becomes A even if the state is B immediately after lighting. In the present invention, constant current control is performed so as to immediately become the state of A when the lighting operation is performed without being in the state of B.

  The constant current control according to the present invention will be described with reference to FIG. A voltage slightly higher than Vf is stored in the microcomputer 5 as a stored value Vmem. Therefore, when the lighting operation is performed by the on / off switch 6 (S1), the constant current control unit 4 causes the voltage across the LED 2 to be in the state shown by C in FIG. 2, that is, constant current so that the voltage across the LED 2 becomes Vmem. Take control. In that state, the current value Ic flows through the LED 2 to emit light strictly, but since the light intensity is extremely small, it can not be recognized by the naked eye that the LED 2 emits light.

  As described above, when the LED 2 is in the energized state, constant current control is performed so that the current value flowing to the LED 2 becomes Ia (S3). As described above, when the current value is increased to Ia, the LED 2 is already in the current-carrying state in which the current value Ic flows, so the state shown in B of FIG.

  When the light on / off switch 6 is turned off (S4), the LED 2 is turned off, but at this time, the LED 2 is not completely turned off but is put in the state of C in FIG. That is, the voltage across the LED 2 is not set to zero but to Vmem (S5). However, it is necessary to continuously correct this stored Vmem due to aging or the like.

  Therefore, it is detected whether current flows through the LED 2 (I = ON) in a state where the voltage across the LED 2 is Vmem (S6), and if current does not flow through the LED 2 in that state, the voltage across both sides The voltage Vmin of the minimum unit is boosted to V, and the boosting is repeated until the current flows to the LED 2 (S6, S7). On the other hand, if the current is flowing through the LED 2, the voltage V across the both ends is decreased by the minimum unit Vmin until the current stops flowing, and this step-down is repeated until the current does not flow through the LED 2 (S8, S9). Then, when the voltage V at both ends is decreased until the current does not flow in the LED 2, a voltage obtained by adding Vmin to the voltage V at which the current does not flow is stored as a new Vmem (S10). The new Vmem becomes a new stored value used in S2 when the on / off switch 6 is turned on next time.

  However, the current continues to flow through the LED 2 although it is weak until the light on / off switch 6 is turned on next. Then, when the timer for which the predetermined time has been set is counted up until the turn-on / off switch 6 is turned on next time (S11), the voltage at both ends is made zero and no current flows in the LED 2 (S12).

  FIG. 4 shows control when the on / off switch 6 is turned on with no current flowing to the LED 2 as described above. When the light on / off switch 6 is turned on (S101), the voltage across the LED 2 is controlled to be the new Vmem stored in S10 (S102), and it is checked whether current flows in the LED 2 in that state. (S103). If current does not flow to LED2, the voltage at both ends is boosted by Vmin until current flows to LED2 (S103, S104), and when current starts to flow to LED2, the control process from S3 is performed I did it.

  The present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention.

1 DC power supply 2 LED
4 Constant current control unit

Claims (3)

  An LED lighting device that applies a DC voltage to the LED to cause the LED to emit light at a predetermined light intensity when the lighting operation is performed, and is a constant voltage that controls the current value flowing to the LED by varying the voltage applied to the LED A control unit is provided, and a current value for causing the LED to emit light at a predetermined light intensity is preset in the constant voltage control unit, and when the lighting operation is performed, the constant voltage control unit causes the current flowing through the LED to be in advance. In the constant current control to achieve the set current value, the constant current control unit is a weak current which can not be recognized by the naked eye that the LED emits light when the lighting operation is performed. An LED lighting device characterized in that the current flowing through the LED is increased from the weak current value to the preset current value when the lighting operation is performed.   The LED lighting device according to claim 1, wherein the constant current control unit corrects a voltage applied to both ends of the LED in a state in which the weak current flows, at the time of a light-off operation.   The constant current control unit cuts off the current to the LED when the lighting operation is not performed within a predetermined time while the weak current is flowing to the LED, and the current to the LED is shut off. When the lighting operation is performed, constant current control is performed such that the weak current flows in the LED, and then the current value of the LED is increased to the preset current value. LED lighting device as described.

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