JP2012150887A - Light-emitting diode lighting control circuit and light-emitting diode lighting control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of noise due to driving of a plurality of colors of light-emitting diodes at the same timing, and to reduce deviation of the tint of lighting generated in a light-emitting diode lighting device.SOLUTION: The light-emitting diode lighting control circuit 103 comprises a timing shuffle circuit 104 which creates a plurality of PWM signals having different timings, respectively, from a plurality of input PWM signals, creates a plurality of sets of PWM signals, where the drive timings of a plurality of colors of light-emitting diodes do not overlap each other, from the plurality of PWM signals thus created, and selects one set out of the plurality of sets thus created.

Description

  The present invention relates to a light emitting diode lighting control circuit and a light emitting diode control method for blinking a plurality of light emitting diodes having different emission colors.

  In recent years, the performance of LEDs has been rapidly improved, and white LEDs that are indispensable for illumination have been developed, and it has become possible to emit light with a brightness that can be used sufficiently as illumination.

  FIG. 6 is a circuit diagram showing a configuration of a conventional light-emitting diode lighting device.

  A light emitting diode lighting device 600 shown in FIG. 6 includes an LED array 621R, an LED array 621G, and an LED array 621B as examples of light emitting diodes of a plurality of colors. The light emitting diode lighting device 600 includes a power supply Vdd1 and a light emitting diode lighting control circuit 603.

  The LED array 621R is composed of a plurality of red-colored LEDs connected in series. The LED array 621G is composed of a plurality of green LEDs connected in series. The LED array 621B includes a plurality of blue LEDs connected in series.

  The power supply Vdd1 is connected to one end of each of the LED array 621R, the LED array 621G, and the LED array 621B. The power supply Vdd1 supplies power to turn on each of the LED array 621R, LED array 621G, and LED array 621B to each of the LED array 621R, LED array 621G, and LED array 621B.

  The light emitting diode lighting control circuit 603 is connected to the other end of each of the LED array 621R, the LED array 621G, and the LED array 621B. The light emitting diode lighting control circuit 603 controls a constant current value supplied to each of the LED array 621R, the LED array 621G, and the LED array 621B.

  The light emitting diode lighting control circuit 603 includes a power MOS transistor 606R, a resistor 604R, a power MOS transistor 606G, a resistor 604G, a power MOS transistor 606B, a resistor 604B, and an LED driver 605.

  The power MOS transistor 606R is connected to the other end of the LED array 621R, the resistor 604R, and the LED driver 605. The power MOS transistor 606G is connected to the other end of the LED array 621G, the resistor 604G, and the LED driver 605. The power MOS transistor 606B is connected to the other end of the LED array 621B, the resistor 604B, and the LED driver 605.

  In FIG. 6, among the LED drivers 605, a circuit for controlling the constant current value flowing through each LED array and a circuit for controlling the luminance of the LED are shown. In addition to the above functions, various functions such as LED open detection and short circuit detection are provided.

  The LED driver 605 includes an operational amplifier 615R, an operational amplifier 615G, and an operational amplifier 615B.

  The operational amplifier 615R supplies a control pulse for controlling the power MOS transistor 606R to the power MOS transistor 606R via the switch circuit 611R.

  The operational amplifier 615G supplies a control pulse for controlling the power MOS transistor 606G to the power MOS transistor 606G via the switch circuit 611G.

  The operational amplifier 615B supplies a control pulse for controlling the power MOS transistor 606B to the power MOS transistor 606B via the switch circuit 611B.

  In the light emitting diode lighting control circuit 603, the operational amplifier 615R, the power MOS transistor 606R, and the resistor 604R constitute a constant current circuit for controlling the constant current value supplied to the LED array 621R.

  The operational amplifier 615G, the power MOS transistor 606G, and the resistor 604G constitute a constant current circuit for controlling the constant current value supplied to the LED array 621G.

  The operational amplifier 615B, the power MOS transistor 606B, and the resistor 604B constitute a constant current circuit for controlling the constant current value supplied to the LED array 621B.

  The constant current value supplied to the LED array 621R is determined by a current determined by the voltage input to VrefR of the operational amplifier 615R and the resistance value of the resistor 604R.

  The constant current value supplied to the LED array 621G is determined by the current determined by the voltage input to VrefG of the operational amplifier 615G and the resistance value of the resistor 604G.

  The constant current value supplied to the LED array 621B is determined by the current determined by the voltage input to VrefB of the operational amplifier 615R and the resistance value of the resistor 604B.

  The light emitting diode lighting control circuit 603 receives a PWM (Pulse Width Modulation) signal from each of PWM_R, PWM_G, and PWM_B.

  The PWM signals supplied from PWM_R, PWM_G, and PWM_B are signals for adjusting the brightness of the LED arrays 621R, 621G, and 621B, respectively. Specifically, the LED arrays 621R, 621G, and 621B are turned on. It is a pulse signal that specifies timing. The control circuits 610R, 610G, and 610B control the brightness of the LED arrays 621R, 621G, and 621B by blinking the LED arrays 621R, 621G, and 621B according to the PWM signals supplied from the PWM_R, PWM_G, and PWM_B, respectively. adjust.

  For example, the control circuit 610R adjusts the luminance of the LED array 621R based on the PWM signal supplied from PWM_R. Specifically, the control circuit 610R turns on the switch circuit 611R and turns off the pull-down transistor 612R during a period (high level period) in which the PWM signal supplied from PWM_R is “H”. As a result, a constant current is supplied to the transistor 606R, and as a result, the LED array 621R is lit.

  On the other hand, during a period (low level period) in which the PWM signal supplied from PWM_R is “L” (low level period), the control circuit 610R turns off the switch circuit 611R and turns on the pull-down transistor 612R. Thereby, the supply of the constant current to the transistor 606R is stopped, and as a result, the LED array 621R is turned off.

  Thus, the light emitting diode lighting control circuit 603 adjusts the luminance of the LED array 621R by blinking the LED array 621R according to the PWM signal supplied from PWM_R. That is, the light emitting diode lighting control circuit 603 increases the brightness of the LED array 621R when the duty ratio of the PWM signal supplied from PWM_R increases, and increases the brightness of the LED array 621R when the duty ratio of the PWM signal supplied from PWM_R decreases. Reduce brightness.

  Similarly, the control circuit 610G adjusts the brightness of the LED array 621G based on the PWM signal supplied from the PWM_G, and the control circuit 610B controls the brightness of the LED array 621B based on the PWM signal supplied from the PWM_B. Adjust.

  In this way, the light emitting diode lighting control circuit 603 adjusts the color of the illumination emitted by the light emitting diode lighting device 600 by adjusting the luminance of each of the LED array 621R, LED array 621G, and LED array 621B.

  In such a light emitting diode lighting device, in order to adjust the luminance of each LED array, as shown in FIG. 7A, a PWM signal having a common cycle (period from tA to tB in FIG. 7) is used. ing. The rise timings of these PWM signals are common, and the duty ratio of each PWM signal is determined by the fall timing of the PWM signal.

  When such a PWM signal is used, for example, as shown in timing tB of FIG. 7A, the rising timing of each PWM signal is aligned every cycle, and all the LED arrays are turned on at the same timing. End up. At this time, a large current is generated in the light emitting diode lighting device, which causes a problem that noise is generated.

  Therefore, in Patent Document 1, FIG. 7B shows a case where the luminance of each of a plurality of light emitting diodes having different emission colors is controlled by a PWM signal for the purpose of preventing the occurrence of such a problem. Thus, a method is described in which the change timing (rise timing and fall timing) of each PWM signal is shifted by a predetermined amount. Thereby, it is said that the generation of noise due to a large current can be reduced without lighting all the LED arrays at the same timing.

JP 2008-91311 A

  However, in the method of shifting the change timing of each LED array as described in Patent Document 1, the overlapping period in which the lighting periods of the LED arrays overlap in each cycle is common. As a result, the light emitting diode lighting device can be used when the LED arrays are blinked according to the PWM signal before the change timing is shifted and when the LED arrays are blinked according to the PWM signal after the change timing is shifted. The problem is that the color of the emitted light is felt differently. That is, it becomes difficult to control the color of illumination emitted by the light-emitting diode lighting device to a color intended for the color (color specified by the PWM signal before shifting the change timing).

  The present invention has been made in view of the above problems, and an object thereof is to prevent the occurrence of noise caused by lighting a plurality of light emitting diodes at the same timing, and to shade the illumination emitted by the light emitting diode lighting device. However, this is to suppress a problem that the color is greatly deviated from the intended color (the color specified by the input PWM signal).

  In order to solve the above-described problems, a light-emitting diode lighting control circuit according to the present invention provides a plurality of light-emitting diodes having different light emission colors according to a PWM signal corresponding to each light emission color and having a common cycle. In the light emitting diode lighting control circuit to be turned on, the high level period of the PWM signal corresponding to each light emission color is shifted so that the overlapping period in which the high level periods of the PWM signal corresponding to each light emission color overlap each other changes in each cycle. It is characterized by having a timing shuffle circuit.

  According to said structure, the lighting timing of several light emitting diodes can be varied by shifting the high level period of the PWM signal corresponding to each luminescent color. Thereby, generation | occurrence | production of the noise resulting from lighting a some light emitting diode at the same timing can be suppressed. Furthermore, according to the above configuration, the overlap period in which the high level periods of the PWM signals corresponding to the respective emission colors overlap is changed for each period, and therefore, the overlap period is common in each period. It is possible to prevent a change in hue.

  In the light emitting diode lighting control circuit according to the present invention, the timing shuffle circuit generates a plurality of intermediate PWM signals having different high level periods by shifting the high level period of the PWM signal corresponding to each light emission color. A combination generation circuit that generates a plurality of combinations of intermediate PWM signals generated from a PWM signal corresponding to each emission color by the PWM signal generation circuit, and a plurality of combinations generated by the combination generation circuit. It is preferable that a combination selection circuit for selecting one combination used for controlling the blinking of the light emitting diodes, and a selection circuit for switching one combination to be selected for each period.

  According to said structure, the timing shuffle circuit which changes periodically the duplication period in which the high level periods of the PWM signal corresponding to each luminescent color overlap can be implement | achieved easily.

  In the light-emitting diode lighting control circuit according to the present invention, the combination generation circuit includes a switch provided on a signal line of the plurality of intermediate PWM signals, and the selection circuit controls the switch to control the plurality of the plurality of intermediate PWM signals. It is preferable to select one combination used to control the blinking of the light emitting diodes.

  According to the above configuration, the combination generation circuit that generates a plurality of combinations of intermediate PWM signals generated from the PWM signals corresponding to the respective emission colors, and the plurality of light emission from the plurality of combinations generated by the combination generation circuit. A combination selection circuit that selects one combination used to control blinking of the diode can be easily realized.

  The selection circuit can be realized by, for example, a pulse generation circuit that generates a pulse signal for controlling the switch.

  In the light-emitting diode lighting control circuit according to the present invention, the PWM signal generation circuit includes a latch circuit that latches a state of the input PWM signal, and uses the latch circuit to output a plurality of intermediate PWM signals having different high-level periods. It is preferable to generate.

  According to said structure, the PWM signal generation circuit which produces | generates several intermediate | middle PWM signals from which a high level period differs can be implement | achieved easily.

  In the light-emitting diode lighting control circuit according to the present invention, the PWM signal generation circuit includes a delay circuit that delays the change timing of the input PWM signal, and a plurality of intermediate PWM signals having different high-level periods using the delay circuit. Is preferably generated.

  According to said structure, the PWM signal generation circuit which produces | generates several intermediate | middle PWM signals from which a high level period differs can be implement | achieved easily.

  In order to solve the above-described problem, a light-emitting diode lighting control method according to the present invention provides a plurality of light-emitting diodes having different emission colors according to a PWM signal corresponding to each emission color and having a common cycle. In the light-emitting diode lighting control method for lighting, the high-level period of the PWM signal corresponding to each light emission color is shifted so that the overlapping period in which the high-level periods of the PWM signal corresponding to each light emission color overlap each other changes in each cycle. A timing shuffling process is included.

  According to said structure, the lighting timing of several light emitting diodes can be varied by shifting the high level period of the PWM signal corresponding to each luminescent color. Thereby, generation | occurrence | production of the noise resulting from lighting a some light emitting diode at the same timing can be suppressed. Furthermore, according to the above configuration, the overlap period in which the high level periods of the PWM signals corresponding to the respective emission colors overlap is changed for each period, and therefore, the overlap period is common in each period. It is possible to prevent a change in hue.

  According to the present invention, it is possible to prevent the occurrence of noise caused by lighting a plurality of light emitting diodes at the same timing, and the hue of illumination emitted by the light emitting diode lighting device is designated by an intended hue (designated by an input PWM signal). Inconveniences such as a large deviation from the above-mentioned color.

1 is a circuit diagram illustrating a configuration of a light-emitting diode lighting device according to Embodiment 1. FIG. FIG. 3 is a circuit diagram illustrating a configuration of a timing shuffle circuit according to the first embodiment. FIG. 6 is a timing diagram illustrating operations of the counter and the shift register according to the first embodiment. It is a figure which shows the relationship between the input and output of a PWM signal used for operation | movement of the light emitting diode lighting device which concerns on Embodiment 1. FIG. FIG. 6 is a circuit diagram illustrating a configuration of a timing shuffle circuit according to a second embodiment. It is a circuit diagram which shows the structure of the conventional light emitting diode lighting device. It is a figure which shows the PWM signal used for operation | movement of the conventional light emitting diode lighting device.

  Hereinafter, a light-emitting diode lighting device according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
First, Embodiment 1 of the light-emitting diode lighting device according to the present invention will be described. 1 is a circuit diagram showing a configuration of a light-emitting diode lighting device according to Embodiment 1. FIG. A light emitting diode lighting device 100 shown in FIG. 1 is a device that lights a plurality of light emitting diodes (LED arrays 621R, 621G, 621B) having different emission colors, similarly to the light emitting diode lighting device 600 shown in FIG. This light emitting diode lighting device 100 is different from the light emitting diode lighting device 600 shown in FIG. 6 in that it includes a light emitting diode lighting control circuit 103 different from the conventional light emitting diode lighting control circuit 603. The light emitting diode lighting control circuit 103 includes an LED driver 105 different from the LED driver 605 included in the diode lighting control circuit 603. The LED driver 105 is different from the LED driver 605 in that it includes a timing shuffle circuit 104. In the following description, the same components as those described above are denoted by the same reference numerals, and the details thereof are omitted.

  The timing shuffle circuit 104 is supplied from PWM_R (hereinafter simply referred to as “PWM_R”), PWM signal supplied from PWM_G (hereinafter simply referred to as “PWM_G”), and PWM_B. By shifting the high level period of the PWM signal (hereinafter simply referred to as “PWM_B”), PWM signals of PWM_Rout, PWM_Gout, and PWM_Bout are generated and output.

  PWM_Rout, PWM_Gout, and PWM_Bout output from the timing shuffle circuit 104 are pulse signals that specify the lighting timing of the LED array 621R, LED array 621G, and LED array 621B. The brightness adjustment of each LED array by each PWM signal is controlled by the control circuit 610R, the control circuit 610G, and the control circuit 610B included in the LED driver 105, similarly to the light-emitting diode lighting device 600 described in FIG.

  For example, the control circuit 610R adjusts the luminance of the LED array 621R based on PWM_Rout output from the timing shuffle circuit 104. Specifically, in a period in which PWM_Rout output from the timing shuffle circuit 104 is “H”, the control circuit 610R turns on the switch circuit 611R and turns off the pull-down transistor 612R. As a result, a constant current is supplied to the transistor 606R, and as a result, the LED array 621R is lit.

  On the other hand, in a period in which PWM_Rout output from the timing shuffle circuit 104 is “L”, the control circuit 610R turns off the switch circuit 611R and turns on the pull-down transistor 612R. Thereby, the supply of the constant current to the transistor 606R is stopped, and as a result, the LED array 621R is turned off.

  In this manner, the control circuit 610R adjusts the luminance (more precisely, the time average value of luminance) of the LED array 621R by blinking the LED array 621R.

  Similarly, the control circuit 610G adjusts the brightness of the LED array 621G based on the PWM_Gout output from the timing shuffle circuit 104. Further, the control circuit 610B adjusts the luminance of the LED array 621B based on the PWM_Bout output from the timing shuffle circuit 104.

  Here, the timing shuffle circuit 104 generates PWM_Rout, PWM_Gout, and PWM_Bout by shifting the high-level periods of PWM_R, PWM_G, and PWM_B, and outputs them.

  Thereby, the generation of noise due to a large current can be reduced without lighting the plurality of LED arrays at the same timing.

  However, since PWM_Rout, PWM_Gout, and PWM_Bout shift the high level period, the overlapping period between the high level periods is different from the overlapping period between the high level periods of the original waveforms PWM_R, PWM_G, and PWM_B. For this reason, if the overlap period in which the high-level periods of PWM_Rout, PWM_Gout, and PWM_Bout overlap is common for each period, the color of the illumination emitted from the light-emitting diode lighting device 100 is caused by this. Shift.

  Therefore, the timing shuffle circuit 104 shifts the high-level periods of PWM_R, PWM_G, and PWM_B so that the overlapping period in which the high-level periods of PWM_Rout, PWM_Gout, and PWM_Bout overlap each other changes every period.

  Thereby, the color shift generated in the illumination emitted by the light emitting diode lighting device 100 is averaged, and the shift is reduced.

  FIG. 2 is a circuit diagram showing a configuration of the timing shuffle circuit 104 according to the first embodiment.

  As shown in FIG. 2, the timing shuffle circuit 104 according to the first embodiment includes DFFs 201, 202, 203, 204, 205, and 206. The timing shuffle circuit 104 according to the first embodiment has a plurality of PWM signals inputted to control driving of light emitting diodes of a plurality of colors by the plurality of D-flip flops (hereinafter referred to as “DFF”). The PWM signal generation circuit is configured to generate a plurality of PWM signals (intermediate PWM signals) having different change timings.

  More specifically, PWM_R input to the timing shuffle circuit 104 is input to the DFF 201. The DFF 201 latches the PWM_R state at the rising edge of the clock signal (hereinafter referred to as “CK”), and generates PWM_R1 delayed from the PWM_R. PWM_R1 is input to the DFF 202. The DFF 202 latches the state of PWM_R1 at the rising edge of CK, and generates PWM_R2 delayed by one clock (one cycle of CK) from PWM_R1. In this way, the timing shuffle circuit 104 generates PWM_R, PWM_R1, and PWM_R2 having different PWM signal change timings.

  The timing shuffle circuit 104 includes a switch 212, a switch 213, and a switch 214. By switching these switches, one of PWM_R, PWM_R1, and PWM_R2 is selected and output to PWM_Rout. For example, since PWM_R is input to the switch 212, when the switch 212 is turned on, PWM_R is output to PWM_Rout. Since PWM_R1 is input to the switch 213, when the switch 213 is turned on, PWM_R1 is output to PWM_Rout. Since PWM_R2 is input to the switch 214, when the switch 214 is turned on, PWM_R2 is output to PWM_Rout.

  PWM_G input to the timing shuffle circuit 104 is input to the DFF 203. The DFF 203 latches the state of PWM_G at the rising edge of CK, and generates PWM_G1 delayed from PWM_G. The PWM_G1 is input to the DFF 204. The DFF 204 latches the state of PWM_G1 at the rising edge of CK, and generates PWM_G2 delayed by one clock from PWM_G1. In this way, the timing shuffle circuit 104 generates PWM_G, PWM_G1, and PWM_G2 having different PWM signal change timings.

  The timing shuffle circuit 104 includes a switch 215, a switch 216, and a switch 217. By switching these switches, one of PWM_G, PWM_G1, and PWM_G2 is selected and output to PWM_Gout. For example, since PWM_G2 is input to the switch 215, when the switch 215 is turned on, PWM_G2 is output to PWM_Gout. Since PWM_G is input to the switch 216, when the switch 216 is turned on, PWM_G is output to PWM_Gout. Since PWM_G1 is input to the switch 217, when the switch 217 is turned on, PWM_G1 is output to PWM_Gout.

  The PWM_B input to the timing shuffle circuit 104 is input to the DFF 205. The DFF 205 latches the state of PWM_B at the rising edge of CK, and generates PWM_B1 delayed from PWM_B. PWM_B1 is input to the DFF 206. The DFF 206 latches the state of PWM_B1 at the rising edge of CK, and generates PWM_B2 delayed by one clock from PWM_B1. In this way, the timing shuffle circuit 104 generates PWM_B, PWM_B1, and PWM_B2 having different PWM signal change timings.

  The timing shuffle circuit 104 includes a switch 218, a switch 219, and a switch 220. By switching these switches, one of PWM_B, PWM_B1, and PWM_B2 is selected and output to PWM_Bout. For example, since PWM_B1 is input to the switch 218, when the switch 218 is turned on, PWM_B1 is output to PWM_Bout. Since PWM_B2 is input to the switch 219, when the switch 219 is turned on, the PWM_B2 is output to the PWM_Bout. Since PWM_B is input to the switch 220, when the switch 220 is turned on, PWM_B is output to PWM_Bout.

  The timing shuffle circuit 104 includes a counter 221 and a shift register 222. Each of the switches 212 to 220 is controlled by a counter 221 and a shift register 222. The counter 221 includes a DFF 207, a DFF 208, and a DFF 209. The shift register 222 includes a DFF 210 and a DFF 211.

  The counter 221 counts up with a second clock signal (hereinafter referred to as “CK2”). In the counter 221, the output of the DFF 207 is A, the output of the DFF 208 is B, and the output of the DFF 209 is S1. The shift register 222 outputs signals S2 and S3 obtained by shifting the signal S1 using A as a shift clock.

  The counter 221 and the shift register 222 are reset by Reset. This Reset is a system reset signal generated when the power is turned on.

  Further, the counter 221 is reset by Reset2 that is an AND output of S1 and B. Note that both of S1 and B become “H” and the counter 221 is reset by Reset2 every time the counter 221 counts the falling edge of CK2 six times.

  Here, operations of the counter 221 and the shift register 222 will be described. FIG. 3 is a timing chart showing the operation of the counter 221 and the shift register 222.

  The counter 221 starts counting at the fall t1 of CK2 after reset by Reset, and at this timing t1, (S1, B, A) = (0, 0, 1). Thereafter, the counters are sequentially counted, and at timing t5, (S1, B, A) = (1, 0, 1). Further, it counts up at the next falling t6 of CK2, and at this timing t6, (S1, B, A) = (1, 1, 0), but as described above, S1 and B are set to “1”. At the moment, reset by Reset2 works, and S1, B, and A all become “0”. As described above, the counter 221 repeats counting from (S1, B, A) = (0, 0, 0) to (S1, B, A) = (1, 0, 1).

  The shift register 222 sequentially shifts S1 output from the DFF 209 to S2 output from the DFF 210 and S3 output from the DFF 211 using A as the output of the DFF 207 as a shift clock.

  Thus, for example, as shown in FIG. 3, when A falls at t6, S1 is reset, so that the DFF 210 outputs “H” to the output S2. Thereafter, S2 holds “H” until the next falling edge t7 of the signal A. At t7, since S1 supplied to the DFF 210 is “L”, S2 output from the DFF 210 is also “L”. However, since S2 supplied to the DFF 211 at the same time is the original “H”, the output S3 from the DFF 211 becomes “H”. In this manner, signals obtained by sequentially shifting the pulse signals of S1 (pulse signals for selecting one combination) are output to S1, S2, and S3.

  As shown in FIG. 2, the switch 212, the switch 215, and the switch 218 are configured to be turned on / off simultaneously by S1. Therefore, during the period when S1 is “H”, the switch 212, the switch 215, and the switch 218 are simultaneously turned on, and PWM_R is output to PWM_Rout. At the same time, PWM_G2 is output to PWM_Gout, and PWM_B1 is output to PWM_Bout. Is done.

  In addition, the switch 213, the switch 216, and the switch 219 are configured to be turned on / off simultaneously by S2. Therefore, during the period when S2 is “H”, the switch 213, the switch 216, and the switch 219 are turned on at the same time, and PWM_R1 is output to PWM_Rout. At the same time, PWM_G is output to PWM_Gout, Is done.

  Further, the switch 214, the switch 217, and the switch 220 are configured to be simultaneously turned on / off by S3. Therefore, in a period when S3 is “H”, the switch 214, the switch 217, and the switch 220 are simultaneously turned on, and PWM_R2 is output to PWM_Rout. At the same time, PWM_G1 is output to PWM_Gout, and PWM_B is output to PWM_Bout. Is done.

  As will be described later with reference to FIG. 4, any of the combinations of PWM_R, PWM_G2, and PWM_B1, the combination of PWM_R1, PWM_G, and PWM_B2, and the combination of PWM_R2, PWM_G1, and PWM_B are combinations that do not overlap the rising timing. Yes.

  Therefore, in the light emitting diode lighting device 100 of the present embodiment, the plurality of switches 212 to 220 have the configuration shown in FIG. It can be said that the function as a “combined generation circuit to be generated” is realized.

  Further, as described above, S1, S2, and S3 are all for “selecting one combination from a combination of a plurality of intermediate PWM signals”. In the apparatus 100, the counter 221 and the shift register 222 that generate and output these S1, S2, and S3 are used as “a selection circuit that selects one combination from a plurality of combinations generated by the combination generation circuit”. It can be said that the function is realized.

  FIG. 4 is a diagram showing the relationship between the input and output of a PWM signal used for the operation of the light-emitting diode lighting device according to the first embodiment.

  4A shows PWM_R, PWM_G, and PWM_B that are PWM signals input to the timing shuffle circuit 104, and PWM_R1, PWM_R2, PWM_G1, PWM_G1, PWM_B1, and PWM signals that are generated by the timing shuffle circuit 104. Each signal with PWM_B2 is shown.

  As shown in FIG. 4A, since the PWM_R, PWM_B, and PWM_G that are input PWM signals have the same period of 6CK, the signals change at the same timing every period (every 6CK). For example, in the example shown in FIG. 4A, all of PWM_R, PWM_B, and PWM_G rise at tB timing, and thereafter rise at the same timing every one cycle (every 6CK). .

  In the example shown in FIG. 4A, the CK timing is set so that CK falls at the timing when all the PWM signals change.

  Therefore, for example, the timing at which CK rises next from the timing at which PWM_R rises becomes the rising timing of PWM_R1.

  Further, the timing at which CK rises next from the timing at which PWM_R rises becomes the rising timing of PWM_R2.

  In the example shown in FIG. 4A, since the high width and low width of CK are equal, PWM_R1 is a signal delayed by 1/2 clock (1/2 cycle of CK) compared to PWM_R. Since PWM_R2 is a signal delayed by one clock (one cycle of CK) from PWM_R1, it is a signal delayed by one and a half cycles from PWM_R.

  The same applies to the relationship between PWM_G and PWM_G1 and PWM_G2, and the relationship between PWM_B and PWM_B1 and PWM_B2.

  FIG. 4B shows signals of PWM_Rout, PWM_Gout, and PWM_Bout that are output during a period when S1 is “H”.

  As already described with reference to FIG. 2, during the period when S1 is “H”, PWM_R is output as PWM_Rout, and at the same time, PWM_G2 is output as PWM_Gout and PWM_B1 is output as PWM_Bout.

  As a result, as shown in FIG. 4B, the PWM signal output as PWM_Gout rises with a delay of one half cycle of CK from the PWM signal output as PWM_Rout. Further, the PWM signal output as PMM_Bout rises with a delay of ½ period of CK from the PWM signal output as PWM_Rout.

  That is, while the input PWM_R, PWM_B, and PWM_G rise at the same timing every cycle (every 6CK), during the period when this S1 is “H”, the output PWM_Rout, PWM_Bout, and The PWMout is changed so as to rise at a different timing for each cycle (every 6 CK).

  FIG. 4C shows PWM_Rout, PWM_Gout, and PWM_Bout signals that are output during a period when S2 is “H”.

  As already described with reference to FIG. 2, during the period when S2 is “H”, PWM_R1 is output to PWM_Rout, PWM_G is output to PWM_Gout, and PWM_B2 is output to PWM_Bout.

  As a result, as shown in FIG. 4C, the PWM signal output as PWM_Rout rises with a delay of ½ period of CK from the PWM signal output as PWM_Gout. Further, the PWM signal output as PMM_Bout rises with a delay of one and a half cycles from the PWM signal output as PWM_Gout.

  That is, the input PWM_R, PWM_B, and PWM_G rose at the same timing every cycle (every 6 CK), while the output PWM_Rout, PWM_Bout, and The PWMout is changed so as to rise at a different timing for each cycle (every 6 CK).

  FIG. 4D shows each signal of PWM_Rout, PWM_Gout, and PWM_Bout output during a period when S3 is “H”.

  As already described with reference to FIG. 2, during the period in which S3 is “H”, PWM_R2 is output to PWM_Rout, PWM_G1 is output to PWM_Gout, and PWM_B is output to PWM_Bout.

  As a result, as shown in FIG. 4D, the PWM signal output as PWM_Rout rises with a delay of one half cycle of CK from the PWM signal output as PWM_Bout. Further, the PWM signal output as PMM_Rout rises with a delay of ½ period from the PWM signal output as PWM_Bout.

  That is, while the input PWM_R, PWM_B, and PWM_G rise at the same timing every cycle (every 6CK), the output PWM_Rout, PWM_Bout, and The PWMout is changed so as to rise at a different timing for each cycle (every 6 CK).

  As described above, the output PWM_Rout, PWM_Bout, and PWMout are every cycle (every 6 CK) in any of the periods when S1 is “H”, S2 is “H”, and S3 is “H”. Each will stand up at a different timing.

  As described above, according to the light-emitting diode lighting control circuit 103 according to the present embodiment, since the rising timings of the plurality of PWM signals are made different, a plurality of light-emitting diodes having different emission colors are simultaneously turned on. This can be prevented, and the generation of noise due to an increase in the amount of change in current can be prevented.

  Here, each LED array is lit while the corresponding PWM signal is “H” period under the control of the light emitting diode lighting control circuit 103. As described above, the timing shuffle circuit 104 changes the timing of each PWM signal, but does not change the length of the “H” period of each PWM signal, that is, does not change the lighting time of each LED array. However, by changing the timing of each PWM signal as described above, a period in which “H” periods (high level periods) of a plurality of PWM signals overlap, that is, a period in which light emitting diodes of a plurality of colors are simultaneously lit. Varies depending on the combination of PWM signals.

  For example, when PWM_Rout, PWM_Gout, and PWM_Bout are all “H”, that is, when all LEDs are lit, as shown in FIG. On the other hand, as shown in FIG. 4B, in the period when S1 is “H”, the time is 2CK. Further, as shown in FIG. 4C, 2.5 CK is obtained when S2 is “H”, and 1.5 CK is obtained when S3 is “H” as shown in FIG. 4D.

  Other than this, the PWM before the timing is changed due to factors such as the relation between PWM_Rout and PWM_Gout, the relation between PWM_Gout and PWM_Bout, the relation between PWM_Rout and PWM_Bout, the period of the PWM signal and the period of CK as the reference for timing change The hue (color appearance) slightly changes between when each LED array is lit with a signal and when each LED array is lit with a PWM signal after timing change.

  Since the PWM signal before the timing change is originally intended to realize the required color tone, the color tone of the illumination actually emitted by each LED array is as much as possible before the timing change is performed. It is preferable to approximate the hue by the PWM signal. However, by changing the timing of each PWM signal, as described above, a deviation in the hue of the light emitted from the light-emitting diode lighting device 100 occurs, and thereafter, the “H” period of each PWM signal overlaps in each cycle. If this value remains constant, this color shift will be perceived.

  Therefore, in the light emitting diode lighting device 100 of the present embodiment, as shown in the timing chart of FIG. 3, the “H” period is periodically changed in the order of S1, S2, and S3. Thereby, in each cycle, the overlap period in which “H” periods of PWM_Rout, PWM_Gout, and PWM_Bout overlap each other periodically changes between the states of FIG. 4 (B) to FIG. 4 (D). As a result, the hue of the illumination emitted by each LED array also periodically changes, and the deviation of the illumination hue emitted by each LED array is averaged and reduced.

  In the present embodiment, an example in which three combinations are generated and periodically switched by the circuit of FIG. 2 has been described. However, four or more combinations may be generated and switched. Good. When the counter is configured to be reset at a 6CK period as in the circuit configuration of FIG. 2, up to six combinations can be switched.

  As described above, according to the light emitting diode lighting device 100 of the present embodiment, by changing the rising timings of the PWM signals so as not to overlap each other, a plurality of light emitting diodes having different emission colors are turned on at the same timing. In addition to preventing the occurrence of noise due to being performed, the overlapping period in which the “H” periods of the PWM signals overlap each other is changed for each period, so that it occurs in the illumination emitted by the light emitting diode lighting device 100. It is possible to reduce the color shift by averaging the color shift.

(Embodiment 2)
Next, a second embodiment of the light emitting diode lighting device according to the present invention will be described. FIG. 5 is a circuit diagram showing a configuration of the timing shuffle circuit 104 according to the second embodiment. In the timing shuffle circuit 104 according to the first embodiment, the configuration example is described in which the timing of each PWM signal is changed by latching the state of each PWM signal by the plurality of DFFs 201 to 206 shown in FIG. The configuration for changing the signal timing is not limited to the configuration using the plurality of DFFs 201 to 206 shown in FIG.

  For example, a configuration in which the timing of the PWM signal is changed by delaying the timing of the PWM signal by a delay circuit, such as the timing shuffle circuit 104 shown in FIG.

  In the example illustrated in FIG. 5, the timing shuffle circuit 104 includes delay circuits 501, 502, 503, 504, 505, and 506. The timing shuffle circuit 104 according to the second embodiment includes a plurality of PWM signals having different change timings from a plurality of PWM signals input to control driving of light emitting diodes of a plurality of colors by the plurality of delay circuits. The PWM signal generation circuit that generates

  More specifically, the PWM signal PWM_R input to the timing shuffle circuit 104 is input to the delay circuit 501. The delay circuit 501 generates PWM_R1 by delaying PWM_R for a predetermined time, and outputs this. PWM_R1 is input to the delay circuit 502. The delay circuit 502 generates PWM_R2 by delaying PWM_R1 for a predetermined time, and outputs this. In this way, the timing shuffle circuit 104 according to the second embodiment generates PWM_R, PWM_R1, and PWM_R2 having different PWM signal change timings.

  The PWM signal PWM_G input to the timing shuffle circuit 104 is input to the delay circuit 503. The delay circuit 503 delays PWM_G for a predetermined time, generates PWM_G1, and outputs this. PWM_G1 is input to the delay circuit 504. The delay circuit 504 delays PWM_G1 for a predetermined time to generate PWM_G2, and outputs this. In this way, the timing shuffle circuit 104 according to the second embodiment generates PWM_G, PWM_G1, and PWM_G2 having different PWM signal change timings.

  Further, the PWM signal PWM_B input to the timing shuffle circuit 104 is input to the delay circuit 505. The delay circuit 505 delays PWM_B for a predetermined time to generate PWM_B1, and outputs this. PWM_B 1 is input to the delay circuit 506. The delay circuit 506 generates PWM_B2 by delaying PWM_B1 for a predetermined time, and outputs this. In this way, the timing shuffle circuit 104 according to the second embodiment generates PWM_B, PWM_B1, and PWM_B2 having different PWM signal change timings.

  Each delay circuit described above may have any configuration as long as it can delay at least the PWM signal. For example, each delay circuit described above can be configured using a resistor, an inverter chain, or the like and having an arbitrary delay time set.

  Also in the light emitting diode lighting device 100 of the second embodiment, similarly to the light emitting diode lighting device 100 of the first embodiment, by changing the change timings of the PWM signals so as not to overlap each other, the light emitting diodes of a plurality of colors Not only can be prevented from being generated at the same timing, but also the change timing of each PWM signal is periodically changed, so that the color shift generated in the illumination emitted by the light emitting diode lighting device 100 can be reduced. The deviation can be reduced by averaging.

  As described above, the first and second embodiments have been described. However, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and each is disclosed in a different embodiment. Embodiments obtained by appropriately combining the technical means provided are also included in the technical scope of the present invention.

  That is, the configuration of the light-emitting diode lighting control circuit is at least “the PWM signal corresponding to each light emission color changes so that the overlapping period in which the high-level periods of the PWM signal corresponding to each light emission color overlap each other changes every period. As long as the function of “shifting the high-level period” can be realized, the circuit configuration described in the embodiment is not limited to that described in each embodiment, and various modifications are made. Anyway. In this case, the function described in each embodiment may be realized by another circuit configuration.

  For example, in the light-emitting diode lighting control circuit described in each embodiment, the function described above is “by shifting the high-level period of the PWM signal corresponding to each emission color, a plurality of intermediate PWM signals having different high-level periods are converted. A PWM signal generation circuit for generating, a combination generation circuit for generating a plurality of combinations of intermediate PWM signals generated from PWM signals corresponding to the respective emission colors by the PWM signal generation circuit, and a plurality of combinations generated by the combination generation circuit A combination selection circuit for selecting one combination used for controlling blinking of the plurality of light emitting diodes from a combination, and a selection circuit for switching one combination selected for each period; Realized, PWM signal generation circuit, combination Various implementations are conceivable for forming circuit, and selection circuit.

  For example, the configuration for realizing the function as the PWM signal generation circuit described above is not limited to the configuration using the plurality of DFFs 201 to 206 shown in FIG. 2 or the plurality of delay circuits 501 to 506 shown in FIG. Other configurations may also be used.

  In addition, the configuration for realizing the function as the combination generation circuit described above is not limited to the configuration using the plurality of switches 212 to 220 illustrated in FIG. 2, and other configurations may be used.

  Further, the configuration for realizing the above-described function as the selection circuit is not limited to the configuration using the counter 221 and the shift register 222 illustrated in FIG. 2, and other configurations may be used.

  The light emitting diodes controlled by the light emitting diode lighting control circuit are not limited to the three LED arrays corresponding to the three colors (RGB) described in the embodiment. For example, the light emitting diode controlled by the light emitting diode lighting control circuit may be three single LEDs corresponding to three colors (RGB).

  In addition, the LED lighting control circuit includes two LED arrays corresponding to two colors or two single LEDs, four or more LED arrays corresponding to four or more colors, or four or more single LEDs, etc. You may comprise so that it may control.

  The present invention can be applied to a light-emitting diode lighting control circuit in which a plurality of light-emitting elements such as LEDs are assembled to constitute one light source, and the light source can be controlled to be lit at an arbitrary brightness as an illumination lamp. it can.

DESCRIPTION OF SYMBOLS 100 Light emitting diode lighting device 103 Light emitting diode lighting control circuit 104 Timing shuffle circuit 105 LED driver 201-206 DFF
212 to 220 Switch 221 Counter 207 to 209 DFF
222 Shift registers 210 to 211 DFF
501 to 506 delay circuit

Claims (7)

In a light emitting diode lighting control circuit for lighting a plurality of light emitting diodes having different emission colors according to a PWM signal corresponding to each emission color and having a common cycle,
A timing shuffle circuit that shifts the high-level period of the PWM signal corresponding to each emission color so that the overlapping period in which the high-level periods of the PWM signal corresponding to each emission color overlap each other changes every period;
A light-emitting diode lighting control circuit. Timing shuffle circuit
A PWM signal generation circuit that generates a plurality of intermediate PWM signals having different high level periods by shifting the high level period of the PWM signal corresponding to each emission color;
A combination generation circuit that generates a plurality of combinations of intermediate PWM signals generated from PWM signals corresponding to the respective emission colors by the PWM signal generation circuit;
A combination selection circuit that selects one combination used to control blinking of the plurality of light emitting diodes from a plurality of combinations generated by the combination generation circuit, and is a selection that switches a combination selected for each period. A circuit,
The light-emitting diode lighting control circuit according to claim 1. The combination generation circuit includes a switch provided on a signal line of the plurality of intermediate PWM signals,
The selection circuit selects one combination used for controlling blinking of the plurality of light emitting diodes by controlling the switch.
The light-emitting diode lighting control circuit according to claim 2. The selection circuit is a pulse generation circuit that generates a pulse signal for controlling the switch.
The light-emitting diode lighting control circuit according to claim 3. The PWM signal generation circuit includes a latch circuit that latches the state of the input PWM signal, and generates a plurality of intermediate PWM signals having different high level periods using the latch circuit. 5. The light-emitting diode lighting control circuit according to claim 4. The PWM signal generation circuit includes a delay circuit that delays the change timing of the input PWM signal, and generates a plurality of intermediate PWM signals having different high-level periods using the delay circuit. The light-emitting diode lighting control circuit according to any one of claims 1 to 4. In the light emitting diode lighting control method of lighting a plurality of light emitting diodes having different light emission colors according to PWM signals corresponding to the respective light emission colors and having a common cycle,
Including a timing shuffle step for shifting the high-level period of the PWM signal corresponding to each emission color so that the overlapping period in which the high-level periods of the PWM signal corresponding to each emission color overlap each other changes in each cycle.
A method for controlling lighting of a light emitting diode.

Images