JP4943891B2 - Light control device and lighting fixture using the same - Google Patents

Description

  The present invention relates to a dimming device that dims an LED and a lighting fixture using the same.

  Conventionally, as a light source for obtaining illumination light, a technique for producing a white color by mixing a plurality of LEDs has been performed by, for example, mixing red, green, and blue, or mixing blue with a yellow phosphor. For the brightness control of the LED, PWM (Pulse Width Modulation) control that mainly controls the temporal duty of current is used. However, since LEDs have high brightness and response time is shorter than that of conventional lamps, when time-division control such as PWM control is performed, the LED signal may blink or flicker when the duty of the PWM signal drops below a certain level. It seemed to be. In order to eliminate this flicker, it is necessary to increase the controllable resolution (minimum adjustment width) and perform finer control. However, since this resolution is determined by the duty of the PWM signal, an attempt to increase the resolution requires PWM control with a high frequency. For this reason, a component including a semiconductor switching element for driving an LED has high performance. It was necessary and the cost was increased. Further, when the frequency of the PWM signal is increased, the absolute value of the maximum duty width is narrowed, so that the adjustable range of the entire LED current is narrowed.

  By the way, as shown in Patent Document 1, it is a lighting device including a lighting circuit for lighting an output from a dimmer with an LED, and the lighting circuit has an output having a switch element and an LED on the input and output sides, respectively. A transformer, a detection circuit that detects the magnitude of the output value of the dimmer and a predetermined value, and controls the operation of the switch element when the detection circuit detects that the output value of the dimmer is lower than the predetermined value A lighting device having a control circuit for stopping or reducing the output of the output transformer is known. However, since this apparatus performs PWM control based on phase control and performs PWM control at a frequency of about 50 Hz to 60 Hz, flickering becomes conspicuous when the dimming lower limit is reached. For this reason, when the output of the dimmer becomes equal to or less than a predetermined value, the LED output is stopped to prevent flickering, so that the dimming range is narrowed and the adjustment function is impaired.

  Further, as disclosed in Patent Document 2, a constant current circuit that drives an illumination light source with a constant current, a constant current switching circuit that switches a constant current value of the constant current circuit, and an illumination light source according to a duty of a PWM signal 2. Description of the Related Art An illumination dimming device including a PWM drive circuit that is controlled in a known manner is known. However, in this device, by changing the current value of the constant current circuit in several steps, the adjustment range is widened by changing the brightness due to the difference in the current value by the same PWM control, but the current value is small However, since the PWM control is basically performed, flickering occurs when the duty becomes a predetermined value or less.

Further, as shown in Patent Document 3, the dimming ratio of the dimming signal included in the power source input to the input circuit is determined, and when the dimming ratio is higher than a predetermined value, PWM control is performed. An LED illumination device is known that expands the adjustment range below a predetermined value by performing peak value control when the value is low. However, since this device performs control by adding peak value control to PWM control by a PWM signal of this dimming ratio when the dimming ratio is equal to or less than a predetermined value, flicker may be visible due to the influence of the remaining PWM control. there were.
JP 2005-11739 A JP 2005-332586 A JP 2005-267999 A

  The present invention has been made to solve the above problem, and in a dimming device that controls the output of an LED by combining PWM control and analog control, the dimming range can be expanded without causing flickering. An object is to provide an inexpensive dimmer.

In order to achieve the above object, a first aspect of the present invention provides a dimming device that controls the output of an LED by combining PWM control and analog control, and a dimming unit that generates a dimming signal for controlling the output of the LED. A control signal generation unit that generates a PWM control signal and an analog control signal based on a dimming signal from the dimming unit, and a current that flows to the LED based on the PWM control signal and the analog control signal from the control signal generation unit An LED control unit that controls current, and the LED control unit generates a DC control voltage corresponding to the analog control signal, and a PWM signal generation unit that PWM-controls the LED current based on the PWM control signal. An analog signal generation unit, and a constant current circuit for direct current control of the LED current by a direct current control voltage from the analog signal generation unit, the LED and PWM signal A generation unit and the constant current circuit is connected in series, the pre-SL control signal generating unit, the stored upper and lower limits of the standard values of the analog control signal, increasing or decreasing the LED luminous intensity by the light control signal when is, when the duty value before Symbol PW M control signal is constant, controlling the analog current flowing said analog control signal increasing or decreasing the reference value of the lower or upper limit to the LED by the LED control unit When the duty value is switched, the analog control signal is controlled to return to the upper or lower reference value, and when the LED output value becomes a predetermined value or less, the output of the LED is controlled. The control is switched to analog control only .

The invention of claim 2 is one provided with a light control device according to 請 Motomeko 1.

According to the first aspect of the present invention, the discontinuous change of the LED current controlled stepwise between the duty of the PWM signal can be complemented and controlled by the analog current, and the dimming resolution is increased (minimum adjustment). The width can be narrowed), so finer high-performance light control can be performed. Thereby, smooth dimming control in which a phenomenon such as flickering does not occur can be performed. In addition, when the duty frequency is the same, the dimming resolution can be made finer and the occurrence of flicker can be suppressed without increasing the frequency of the PWM signal, so the frequency performance is low for LED driving. Since semiconductor elements and electrical components can be used, the light control device can be made inexpensive. Furthermore, since the frequency of the PWM signal can be lowered, the period of the PWM signal can be increased, so that the control width by the PWM signal is increased and the dimming range can be expanded. Further, when the output value of the LED becomes equal to or lower than the predetermined value, it can be controlled only by analog control without performing the PWM control. Therefore, by setting the predetermined value to, for example, the duty of the dimming lower limit, near the dimming lower limit The light can be dimmed without causing flicker.

According to the second aspect of the present invention, since it can be configured by using a dimming device capable of increasing the dimming resolution without increasing the duty frequency of the PWM signal, the lighting with a wide dimming range and less flickering is possible. A lighting device that realizes control can be provided at low cost.

Hereinafter, a light control device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block configuration of the light control device of this embodiment. As shown in FIG. 1, the dimmer device includes an LED 1, a dimmer 2, a control signal generator 3, a PWM controller 4, an analog controller 5, an LED controller 6, and a drive power supply circuit 7. The LED control unit 6 includes a PWM signal generation unit 8, an analog signal generation unit 9, and a constant current circuit 10.

  In this dimming device, a control signal generator 3 generates a PWM control signal and an analog control signal based on a dimming signal K from the dimmer 2, and the PWM control signal and analog control from the control signal generator 3 are controlled. The PWM control unit 4 and the analog control unit 5 are controlled by the signal, respectively, and the PWM control unit 4 and the analog control unit 5 control the LED control unit 6 to control the current flowing through the LED 1 by combining PWM control and analog control. To do.

  The LED 1 is an illumination light source including a plurality of light emitting diodes D1, D2, D3. The LED 1 is supplied with power from a DC stable power supply E such as a battery, and the drive power supply circuit 7 is driven by the DC stable power supply E to generate a power supply voltage Vcc, and this power supply voltage Vcc is supplied to other circuit units. Supply.

The dimmer 2 outputs a dimming signal K (K _{0 to} K5) and transmits it to the control signal generator 3 as shown in FIG. The dimming signal K, the ratio of pulse on-time of the PWM signal (hereinafter, referred to as duty) expressed in, here, for example, a duty 80% of _{K 0,} the K + 5 as a duty 85 _{(%), K} 0 ~ The dimming resolution is finely set so that the 1% unit width is the minimum adjustment width between K5. In this dimming, the dimmer 2 increases the duty of the dimming signal K when the dimming level is high, and outputs the PWM signal for the dimming signal that decreases the duty when the dimming level is low. Output.

The control signal generator 3 is formed by a CPU (not shown), and based on the dimming signal K from the dimmer 2, a PWM signal P (PWM) for PWM-controlling the output of the LED 1 in accordance with the dimming level. a control signal), generates each control signal of the analog control signal a (analog control signal) for analog control of the output of LED1.

The PWM signal P is a PWM signal that is formed based on the dimming signal K and is represented by a duty N (N ₀ , N + 1, N + 3...) That is a pulse signal having a minimum adjustment width larger than that of the dimming signal K. . Here, the minimum adjustment width of the PWM signal P is set between adjacent duties, for example, the interval between the duty N ₀ and the next duty N + 1. Further, the control signal generator 3 presets a duty N corresponding to the dimming signal K based on the dimming signal K. Table 1 shows a relationship among the dimming signal K, the duty N of the PWM signal P, and the analog control signal A. Here, the duty corresponding duty corresponding to the dimming signal K ₀ to N _0, dimming signal K5 is set to N + 1. The relationship between the duty N and the dimming signal K is dimming signal _{K 0} (e.g., a duty of 80%) made to correspond to duty _{N 0} for the same duty 80%, the dimming signal K5 (e.g., duty 85%) is associated with a duty N + 1 with a duty of 85%. The dimming signals K _{0 to} K 5 correspond to duty positions that divide the duty N ₀ and the duty N + 1 into five equal parts. Further, the control signal generator 3 generates analog control signals A _{0 to} A5 of DC signals corresponding to the dimming signals K _{0 to} K5 divided into five equal parts. Here, the analog control signal A5 in duty N + 1, when the dimming signal K becomes K + 5, is set to be the same value as the analog control signal A ₀ at the duty N. The PWM signal P and the analog control signal A thus formed are output to the PWM control unit 4 and the analog control unit 5, respectively, and control these control units.

PWM control unit 4, as shown in FIG. 3, formed by L S I41, based on the PWM signal P (duty N) from the L S control signal generator 3 is input to I41, LED control unit 6 PWM signal Q for controlling the signal is output to the PWM signal generation unit 8 of the LED control unit 3. Here, the duty of the PWM signal Q is substantially the same as the duty N of the PWM signal P.

The analog control unit 5 outputs an analog control signal B for analog control of the LED control unit 6 based on the analog control signal A from the control signal generation unit 3. The analog control signal B is a DC voltage signal proportional to each of A _{0 to} A 5 of the analog control signal A, and is input to the analog signal generation unit 9 of the LED control unit 6 .

In the LED control unit 6 , the PWM signal generation unit 8 includes a switching semiconductor element (FET) Tr1 connected between the LED 1 and the ground (or voltage source) as shown in FIG. The PWM signal generation unit 8 performs PWM control of the output current I of the LED 1 by turning on and off Tr1 according to the duty of the PWM signal Q during the period in which the LED 1 is current-controlled by the PWM signal Q from the PWM control unit 4. .

Further, the analog signal generation unit 9 in the LED control unit 6 is connected to the analog control signal B from the analog control unit 5 and generates a DC control voltage corresponding to the analog control signal B. The constant current circuit 10 is controlled by the DC control voltage output from the analog signal generation unit 9 and performs analog control of the current flowing through the LED 1.

  The dimming control of the present embodiment having the above configuration will be described with reference to FIGS. 4 (a) to 4 (d) and FIG. FIG. 4 shows an outline of the dimming control. FIG. 4A shows the change in the approximate luminous intensity of the LED 1 PWM-controlled by the PWM control unit 4 with the duty N, and FIG. 4A shows an enlargement of the A part, FIG. 4C shows a change in luminous intensity due to the analog current control of the LED 1 of the analog control part 5, and FIG. 4D shows the luminous intensity of the PWM control by the PWM control part 4. The state where the change is complemented by the analog control of the analog control unit 5 is shown.

This light control will be described in more detail with reference to FIG. Here, as shown in FIG. 5 (a), 5 out of different dimming signal K duty to dimmer 2 from the dimming signal K ₀ dimming signal K + 5 is transmitted thereto. These dimming signals K _{0 to} K + 5 have the same duty difference between the adjacent dimming signals K. Control signal generating unit 3, as shown in FIG. 5 (b), generates an analog control signal A out of 5 from A ₀ corresponds to A + 5 from these dimming signal K ₀ to K + 5. Here, the analog control signal A is divided into five equal parts corresponding to the dimming signals K _{0 to} K + 5 between A ₀ and A + 5 to control the analog control unit 5. Further, as shown in FIG. _{5 (c), K 0,} K + 5 in the dimming signal K corresponds to the duty _N 0, N + 1 in the PWM signal P, corresponding to these duty _N 0, N + 1, the LED1 The luminous intensity L is luminous intensity L ₀ and luminous intensity L + 1, respectively.

The control signal generation unit 3 (see FIG. 1) controls the adjustment value of the analog control unit 5 (here, the analog control unit 5 is controlled) for adjusting the luminous intensity of the LED 1 by the analog control unit 5 based on the analog control signal A in advance. in the upper limit value Aa (wherein the analog control signal a) is to be, a + 5 corresponds to) the lower limit value Ab (here and, corresponding to _{a 0)} stores. The analog current flowing through the LED 1 in conjunction with the upper limit value Aa and the lower limit value Ab has an upper limit value Ia and a lower limit value Ib. It will have the value Lb. However, as will be described later, when the level of the dimming signal K increases, the control signal generator 3 returns the upper limit value Aa to the lower limit value Ab when the dimming signal K + 5 is detected. Correspondingly, the upper limit value Ia and the upper limit value La return to the lower limit value Ib and the lower limit value Lb. Further, when the level of the dimming signal K decreases, the operation reverse to these is performed.

In FIG. 5B, the horizontal axis represents the analog control signal A, and the vertical axis represents both the analog current I and the light intensity L that change in accordance with the analog control signal A, and the analog current changes in Ia and Ib. In addition, the light intensity L changes from the lower limit value Lb to the upper limit value La. Here, the reference values Aa and Ab of the analog control signal A correspond to A ₀ and A + 5 in Table 1, and the difference ΔA between the reference values Aa and Ab (between A ₀ and A + 5) is the adjustment of the analog control signal A. It becomes width. The current change between the analog currents Ia and Ib of the LED 1 corresponding to the adjustment width ΔA of the analog control signal A is ΔI, the light intensity change is ΔL, and the current change ΔI and the light intensity change ΔL are respectively adjusted by analog control. The adjustment width. Further, these adjustment widths are equally divided into five by the analog control signals A _{0 to} A5 corresponding to the dimming signals K _{0 to} K + 5, and the adjustment interval is performed in five stages. These adjustment widths are all the same between the duties N, but can be individually set according to each duty. For example, the adjustment width ΔI or ΔL can be increased when the duty of the PWM signal P is large, and the adjustment width ΔL can be decreased when the duty is small.

Under the set conditions of the respective reference value, the control signal generating unit 3, modulating the light controller 2 dimming signal K ₀ ~K + 5 is sent, five percentage for each duty set in advance, for example, K ₀ When (80%) and K + 5 (85%) are detected, a PWM signal P having a duty of N ₀ and N + 1 is generated.

Here, when the luminous intensity of the LED 1 is increased, for example, a case where K + 1 (81%) is detected in the state of K ₀ (80%) is considered. The control signal generator 3 already forms a PWM signal P with a duty N _{0 in} the state of K ₀ (80%), and controls the PWM controller 4 and the LED controller 6 based on the PWM signal P. are PWM controlled LED1 current duty _{N 0.} When detecting the dimming signal K + 1 (81%), the control signal generating unit 3 increases the luminous intensity of the LED 1 from K ₀ (80%) to K + 1 (81%) according to the dimming signal K + 1. Therefore, when the control signal generating unit 3 detects the duty 81% of the dimming signal K + 1 (81%), the level of the analog control signal A is set to the upper reference value Aa based on the analog control signal A + I in Table 1. Then, the analog controller 5 is controlled to increase the analog current of the LED 1 and increase the luminous intensity of the LED 1.

Further, as the duty of the dimming signal K increases to K + 2, K + 3, K + 4, the level of the analog control signal A to the analog control unit 5 is increased toward the reference value Aa, and the analog current of the LED 1 is increased. When the light control signal K becomes K + 5 and the level of the analog control signal A reaches the upper limit reference value Aa (A = A + 5), the control signal generator 3 increases the duty of the PWM signal P that performs PWM control. And the level of the analog control signal A is returned to the lower limit reference value Ab. As a result, the analog current I flowing through the LED 1 also returns to the current value Ib. That is, as shown in Table 1, the dimming signal K analog control is increased from K ₀ to K4, becomes a K5, the duty of the PWM signal P with increasing from N ₀ to N + 1, the analog control signal A The upper limit reference value Aa is returned to the lower limit reference value Ab, and analog control is again performed in response to the next dimming signal K.

Next, when the luminous intensity of the LED 1 is decreased, the control signal generation unit 3, for example, controls the dimmer 2 when the dimming signal K is K + 5 and the duty of the PWM signal P is N + 1, as described above. When the dimming signal K from K + 5 changes from K + 5 to K + 4, the control signal generator 3 determines that the light intensity of the LED 1 is decreased, generates an analog control signal A + 4 corresponding to K + 4, and the level of the analog control signal A Is reduced toward the lower limit reference value Ab, whereby the analog control unit 5 decreases the analog current of the LED 1 to decrease the luminous intensity of the LED 1. When the dimming signal K becomes K ₀ , the duty of the PWM signal P is decreased from N + 1 to N, the analog control signal A is shifted from the lower limit reference value Ab to the upper limit reference value Aa, and thereafter the same operation is performed. repeat.

  As described above, the dimming control by the dimming device increases the duty of the dimming signal K when the duty N of the PWM signal P remains constant when the dimming signal K increases or decreases. Or, in proportion to the rate of decrease, the analog current is sequentially increased or decreased from the upper reference value Aa or the lower reference value Ab of the analog control signal A, and when the duty N is changed, each reference value is restored to the original state. Let me return to Thereby, the digital change of the current between the duty N can be made analog to suppress discontinuity.

  As described above, according to the light control device of the first embodiment, the discontinuous change in the current of the LED 1 controlled stepwise between the duties of the PWM signal P can be complemented and controlled by the analog current. Therefore, the resolution (minimum adjustment width) of dimming can be increased, and finer high-performance dimming control can be performed. Thereby, smooth dimming control in which a phenomenon such as flickering does not occur can be performed. In addition, when the duty frequency is the same, the dimming resolution can be made finer, and flickering can be suppressed without increasing the frequency of the PWM signal, so the frequency performance is low for LED driving. Since semiconductor elements and electrical parts can be used, the cost can be reduced. Furthermore, since the frequency of the PWM signal can be lowered, the period of the PWM signal can be increased, so that the control width by the PWM signal is increased and the dimming range can be expanded.

  Next, a dimming device according to a second embodiment of the present invention will be described with reference to FIGS. 6, 7A and 7B. The configuration of this embodiment is basically the same as that of the above embodiment, and a part of the output of the LED control unit is fed back to the control signal generation unit, and the target output of the LED current set by the dimmer with the dimming signal The value is compared with the LED output value of the LED in the operating state, and based on the comparison result, the LED current is controlled by the analog control unit, and the LED output value is controlled to match the target set value. Unlike the first embodiment, the others are the same.

FIG. 6 shows a circuit configuration block of the light control device of this embodiment. A detection output value Z, which is a part of the output of the LED control unit 6, is fed back to the control signal generation unit 3 and compared with the PWM signal of the LED 1 corresponding to the dimming signal K. The detected output value Z is an output signal proportional to the LED output value of the LED 1 in the LED control unit 6 , and is adjusted in advance by normalization or the like so that it can be easily compared with the target output value Y.

Table 2 shows the relationship of LED output target output values Y (Y ₀ , Y1, Y2) corresponding to preset dimming signals K (K ₀ , K1, K2), and Table 3 shows the PWM signal It shows the relationship between the LED output value _{X (X 0, X1, X2} ) corresponding to the tee - duty _{NN (0, N + 1,} N + 2) and these du.

  The control signal generation unit 3 previously obtains the LED output target value of the dimming signal K shown in Table 2 and the LED output value of the LED 1 corresponding to the duty N of the PWM signal P by the PWM control unit 4 shown in Table 3. Remember each one. This LED output value is an output characteristic from the LED control unit 6 to the LED 1, and specifically indicates an output voltage and output power.

In the above configuration, the control signal generation unit 3 first calculates the target output value Y (Y ₀ , Y + 1, Y + 2) corresponding to the dimming signal K (here, K ₀ , K + 1, K + 2) as the duty of the PWM signal P. Compared with LED output values X (X ₀ , X ₁ , X 2) corresponding to N (N ₀ , N + 1, N + 2), the duty N (N ₀ , N + 1, N + 2) of PWM control is set.

As shown in FIGS. 7A and 7B, when the light intensity is increased in dimming (for example, when the duty of the dimming signal K is increased), the dimming signal K from the dimmer 2 is used. When K is K _0, the target output value is Y ₀ from Table 2, so the target output value Y ₀ is compared with the LED output value X. Here, when X ₀ <Y ₀ <X1, the duty N of the PWM signal is set to duty N ₀ (signal corresponding to the output value X1). Then, by comparing the detected output value Z and the target output value Y ₀ from the LED control section 6 by the control signal generating unit 3, based on the difference between the LED output value Y ₀ and the detected output value Z, an analog controller 5 Control and adjust the current. Then, the control signal generating unit 3 controls so that the detected output value Z increases from the difference ΔXa amount corresponding LED output value X ₀ of the target output value Y _0, the detection output value Z approaches the target output value Y ₀ Thus, the LED control unit 6 is controlled.

Next, when dimming the light intensity by dimming, for example, when the dimming signal K is K ₀ and the target output value Y ₀ is X ₀ <Y ₀ <X ₁ , The duty is N + 1 (LED output value X1 equivalent signal). Control signal generating unit 3 performs a comparison between the target output value Y ₀ corresponding to detection output values Z and dimming signal K ₀ from the LED control unit 3, the current adjustment of the analog control, a target from the LED output value X1 controlled so as to reduce the output value Y ₀ by the difference ΔXb amount detection output value Z, the detection output value Z controls the analog control unit 5 so that the target output value Y1.

As described above, according to the second embodiment, the control signal generator 3 compares the detected output value Z from the LED controller 6 with the target output value Y, and adjusts the LED output by adjusting the current of analog control. can be controlled to increase or decrease the value X from X ₀ or X1, controls the analog control unit 5 so that the target output value Y1 to be dimmed detection output value Z. As a result, the duty N of the PWM control can be finely adjusted without increasing the adjustment accuracy. By comparing the target output value Y and the detected output value Z, fine control can be performed based on the actual measurement result of the LED output value. Therefore, control close to the dimming setting target is possible.

  Next, a light control device according to a third embodiment of the present invention will be described. Since the configuration of the present embodiment is basically the same as that of the first embodiment, the drawings are omitted. In the light control device of the present embodiment, the control signal generator switches the control of the LED output to only the analog control when the LED output value becomes a predetermined value or less.

  When the duty N of the PWM signal falls below the set duty Nr, the control signal generator 3 (see FIG. 1) sets the duty of the PWM signal P applied to the PWM controller 4 to 100%, eliminates PWM control, and performs analog control. The LED control unit 6 is controlled only by analog control by the unit 5. Here, the set duty Nr is a duty value larger than the duty at which the LED 1 feels flickering. For example, when the flickering duty of the LED 1 is α, the duty Nr is α + 1.

  The control signal generation unit 3 has an analog control value (Vr) for controlling the LED 1 by the analog control unit 5 when the duty is Nr, a duty value Nmin at which the dimming intensity is a minimum value, and analog control at that time The value (Vmin) is stored in advance. Then, the difference Vr−Vmin between the analog control value Vr and the analog control value Vmin is divided by the duty difference (Nr−Nmin) between the duty Nr and the duty value Nmin, and the analog control value for each duty obtained by this division is divided in advance. Remember. For example, if the duty Nr is 20% and the duty value Nmin is 10%, Vr−Vmin is equally divided into 10 and all analog control values corresponding to duty values equal to or less than the duty Nr are stored.

  In the state set in this way, when a dimming signal K having a duty Nr or less is input, the control signal generator 3 calls an analog control value corresponding to the duty of the dimming signal K, and this analog control value is The analog control unit 5 can be controlled as an analog control signal to control the current of the LED 1. The duty value Nmin indicates a state just before the illumination of the LED 1 is turned off, and the duty value or the analog control value Vmin is not necessarily zero. Further, the method of setting the duty to 100% can be performed either when the PWM control unit 4 is controlled with 100% duty or when the PWM control unit 4 is turned off. Note that when the ambient temperature is low, the forward voltage of the LED 1 increases, and therefore, if the PWM signal is adjusted with the amplitude lowered, the LED 1 may not be lit. The current of the LED 1 is adjusted in a state where is kept constant.

  As described above, according to the dimming device of the third embodiment, the predetermined duty Nr is set to a duty just before the flicker starts to occur, so that when the duty of the dimming signal is less than the duty Nr, the PWM control unit 4 Can be PWM controlled at approximately 100%, and the current of the LED 1 can be analog controlled in proportion to the duty of the dimming signal. As a result, even when the duty of the PWM signal becomes small near the dimming lower limit where the LED 1 is dimmed, the dimming can be performed so as not to cause a phenomenon such as LED flickering while maintaining the dimming gradation. it can. The same effect can be obtained even if the duty of the PWM signal for controlling the PWM controller 4 is not 100%.

  The present invention is not limited to the configuration of each of the above embodiments, and various modifications can be made. For example, in the above-described first embodiment, the reference value of the analog control signal is provided and controlled on the upper limit side and the lower limit side, but the reference value is provided between the upper limit side and the lower limit side, and this intermediate value is used as the reference value. By controlling symmetrically up and down, the control amplitude width can be reduced by half.

The block block diagram of the light modulation apparatus which concerns on the 1st Embodiment of this invention. (A), (b) is a figure explaining the relationship between the light control signal and PWM signal of an apparatus same as the above. The figure which shows the circuit example of the PWM control part and PWM signal generation part of an apparatus same as the above. (A) is a figure which shows the approximate luminous intensity characteristic of LED with respect to the duty by PWM control, (b) is an enlarged view of the A section of (a), (c) is a figure which shows the approximate luminous intensity characteristic of LED by analog control (D) is a figure which shows the rough luminous intensity characteristic of LED with respect to the duty by PWM control and analog control. (A) is a figure which shows the duty of a light control signal, (b) is a figure explaining the analog current complement of the LED current by an analog control signal, (c) is a figure which shows the rough luminous intensity characteristic of LED by which the analog complement was carried out. The block block diagram of the light modulation apparatus which concerns on the 2nd Embodiment of this invention. (A) is a figure explaining the complementation by the analog control of LED output value by PMW control of the same apparatus, (b) is a figure which shows the relationship between the light control signal of the same apparatus, and the target output value of LED.

Explanation of symbols

1 LED
2 Light control unit 3 Control signal generation unit 4 LED control unit

Claims (2)

In the dimming device that controls the output of the LED by combining PWM control and analog control,
A dimming unit for generating a dimming signal for output control of the LED;
A control signal generator for generating a PWM control signal and an analog control signal based on a dimming signal from the dimming unit;
An LED control unit that controls a current flowing through the LED based on a PWM control signal and an analog control signal from the control signal generation unit, and
The LED control unit includes a PWM signal generation unit that PWM-controls an LED current based on the PWM control signal, an analog signal generation unit that generates a DC control voltage corresponding to the analog control signal, and the analog signal generation unit. A constant current circuit for direct current control of the LED current with a direct current control voltage of
The LED, the PWM signal generator, and the constant current circuit are connected in series,
Before SL control signal generating unit, the stored upper and lower limits of the standard values of the analog control signal, when the increase or decrease the luminosity of the LED by the light control signal, the duty value before Symbol PW M control signals When it is constant, the analog control signal is increased or decreased from the lower limit or upper limit reference value to control the analog current flowing in the LED by the LED control unit, and when the duty value is switched, the analog control signal The dimming is characterized in that the signal is controlled to return to the upper limit or lower limit reference value, and when the LED output value becomes a predetermined value or less, the LED output control is switched to analog control only. apparatus. A lighting fixture comprising the light control device according to claim 1 .

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