JP2010118194A - Led lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED lighting device capable of superposing communication signals in free and easy extraction on on-off pulses of PWM control, in case LEDs are put under luminance adjustment by the PWM control. <P>SOLUTION: The communication signals including luminance information of the LEDs 1 sent from a lighting part 2 via a power source cable W to a lighting drive part 3 in superposition on the on-off pulses of the PWM control are taken out at off-pulse time of the PWM control, so that the communication signals can be precisely taken out as driving current is low at the LED lighting off time as compared with extraction at on-pulse time at the LED lighting time. Therefore, communication signals can be superposed in free and easy extraction on the on-off pulses of the PWM control in a simple structure, without taking trouble to separately add other cables. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an LED lighting device that includes an LED and adjusts the luminance of the LED by PWM control.

  Conventionally, as shown in FIG. 6A, an illumination unit 52 having a light emitting diode (LED) 1 and an illumination drive unit 53 that drives the illumination unit 52 are provided. For example, in the PWM (Pulse Width Modulation) control method, the voltage supplied to the illumination unit 52 is adjusted by varying the on / off pulse width of the supply voltage as shown in FIG. LED lighting devices are known (for example, Patent Document 1).

  By the way, as for this LED lighting apparatus, the brightness | luminance of LED1 fluctuates with a temperature change, and the brightness | luminance of LED1 falls gradually by a secular change. When it is necessary to automatically correct the luminance of the LED 1, as shown in FIG. 7, two illumination units (illumination units with correction) 62 and illumination drive units (drive units with correction) 63 with connectors C are provided. The luminance information of the LED 1 obtained by receiving the entire LED or a part of the light projection state on the illumination unit 62 side is transmitted to the illumination drive unit side, and the illumination drive unit 63 Based on the information, the on-pulse width of PWM control and the output voltage are corrected so that the luminance of the LED 1 becomes the target luminance.

  In the LED lighting device of FIG. 7, the illumination unit 62 detects the light projection state of the LED 1 as the amount of received light, and obtains luminance information. The transmission circuit 72 includes a transmission circuit 72 for transmission, and the illumination driving unit 63 includes a reception circuit 73 that receives the luminance information, and a correction circuit 74 that corrects the luminance of the LED 1 based on the luminance information. In addition to the two power cables W, it is necessary to separately wire two cables W1 with connectors C1 as the power lines to the light receiving circuit 71 and the transmission circuit 72 and the communication lines of the transmission circuit 62. It becomes.

  However, there is a case where it is desired to provide compatibility between devices in each use state depending on whether it is necessary to correct the brightness of the LED 1 or not. In this case, as shown in FIGS. 8 (A) and 8 (B), the unnecessary connector C1 of the two cables W1 is left over, so that the illumination unit 62 is used using the two power cables W. It is conceivable to superimpose the communication signal of the transmission circuit 72 and the power supply supplied to the light receiving circuit 71 and the transmission circuit 72 on the power supply supplied to.

By the way, various communication means for superimposing a communication signal on a power supply to be supplied are conventionally known. Examples of this include power line communication for superimposing a communication signal on a commercial AC power supply (for example, Patent Document 2), and call voice. An intercom (for example, Patent Document 3) that outputs a DC power supply superimposed on a communication line that transmits the signal is cited. In Patent Document 2, the communication signal is superimposed on the commercial AC power supply frequency 50-60 Hz, and in Patent Document 3, the DC power supply is superimposed on each other. Therefore, since there are few noise components included in the communication signal, accurate extraction (restoration) is possible. It becomes possible.
JP 2008-1212796 A JP 2008-160490 A JP 2008-28866 A

  However, when adjusting the brightness of the LED by PWM control, the PWM signal for turning on the LED is normally repeatedly turned on and off at a high frequency of about 20 to 100 kHz, and the voltage and current is about 12 V, several tens of mA to several A, In addition, since it includes a lot of harmonic components due to the rectangular wave, it is difficult to accurately extract the superimposed communication signal.

  For example, when an LED illumination device is used for the image processing device, as shown in FIG. 9, it is repeatedly turned on and off according to shooting, image processing, and a standby state, and is turned on only when necessary. There are many cases of intermittent drive. When the light is turned off, power is not supplied to the light receiving circuit / transmission circuit on the illumination unit side.

  The present invention solves the above-described problems and provides an LED lighting device capable of easily superimposing a communication signal on an on / off pulse of PWM control so that the brightness of the LED is adjusted by PWM control. It is an object.

  In order to achieve the above object, an LED lighting device according to the present invention is connected to an illumination unit having an LED, the illumination unit and two power cables, and has an on / off pulse width of a supply voltage from a DC power supply unit. An illumination drive unit that adjusts a voltage supplied to the illumination unit by PWM control to vary and drives the LED to light up so that brightness can be adjusted, and communicates from the illumination unit to the illumination drive unit via the power cable Communication means, wherein the communication means performs communication by superimposing a communication signal including at least luminance information of the LED on an on / off pulse of the PWM control, and the illumination driving unit is configured to communicate with the communication unit. An information extraction means is provided for extracting a communication signal including the luminance information, which is output when the PWM control is turned off.

  According to this configuration, since the communication signal including the luminance information of the LED that is communicated by being superimposed on the on / off pulse of the PWM control from the illumination unit to the illumination drive unit via the power cable is extracted at the time of the off pulse of the PWM control, the LED Since the drive current is lower when the LED is turned off than when it is turned on when it is turned on, the communication signal can be taken out accurately, so PWM can be done with a simple configuration without increasing the number of other cables. It is possible to superimpose the communication signal on the control ON / OFF pulse so that it can be easily taken out.

Preferably, the illumination unit detects a light projection state of the entire LED or a part of the LED as a received light amount and obtains the luminance information, and a transmission circuit that transmits a communication signal including the luminance information to the illumination driving unit. And a signal generation circuit that generates a communication signal including the luminance information to be transmitted from the transmission circuit based on a change in current consumption of the illumination unit corresponding to the luminance information obtained by the light receiving circuit. The illumination driving unit further includes a receiving circuit that receives the communication signal including the luminance information transmitted from the lighting unit; and the luminance information received by the receiving circuit and extracted by the information extracting unit. And a correction circuit that corrects the brightness of the LED based on a communication signal that is included. Here, the consumption current of the illumination unit refers to a load current consumed by the load of the entire illumination unit during the PWM control off-pulse.
Therefore, it is possible to easily superimpose the communication signal on the PWM control on / off pulse with a simpler configuration, and it is possible to easily correct the luminance of the LED based on the extracted communication signal.

  Preferably, the voltage supplied to the illumination unit at the time of the PWM control on-pulse is an average luminance when the LED of the illumination unit is continuously lit and there is no off-pulse time even when the PWM control off-pulse time exists. The voltage is set to maintain the same luminance. Therefore, when the communication signal including the luminance information is extracted during the PWM control off-pulse, the illumination unit can obtain the same luminance as that during continuous lighting.

  Preferably, the voltage supplied to the illumination unit at the time of the PWM control off-pulse is set to a voltage at which the transmission circuit and the light receiving circuit can be driven and the LED is not lit even when supplied. Therefore, even during the PWM control off pulse when the LED is turned off, the voltage can be supplied to the transmission circuit and the light receiving circuit of the illumination unit so that the LED can be operated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an LED lighting device according to an embodiment of the present invention. The apparatus is connected to, for example, an illuminating section (illuminating section with correction) 2 having a plurality of LEDs 1 and two power cables W with connectors C to supply power to the illuminating section 2. From the illumination unit 2, an illumination drive unit (drive unit with correction) 3 that drives the LED 1 by adjusting the voltage supplied to the illumination unit 2 by PWM control that varies the on / off pulse width of the LED 1, and lights the LED 1 so that the brightness can be adjusted. The communication means 4 which communicates with the illumination drive part 3 via the power cable W is provided.

  The communication means 4 communicates by superimposing a communication signal including at least luminance information of the LED 1 on the on / off pulse of the PWM control. In this example, the communication signal is a communication signal including the luminance information of the LED 1, but in addition, a temperature sensor such as a thermistor may be provided in the vicinity of the LED 1 to use the temperature information of the LED 1 as a communication signal. Both information and temperature information may be used as communication signals.

  The illumination drive unit 3 includes a DC power supply unit (constant voltage power supply) 5 that is a DC power supply source, a PWM control unit 6, information extraction means 7, a reception circuit 8 / correction circuit 9, and a first drive power supply 10. ing.

  The PWM control unit 6 turns on the LED 1 according to the desired lighting state of the PWM oscillation circuit 21, the AND circuit 22, the switching transistor 23, and the LED 1 that constantly oscillates an on / off signal at a constant frequency of about 20 to 100 kHz, for example. And an external lighting control input 24 for commanding the timing of extinction from the outside.

  When the AND circuit 22 receives both the input from the PWM oscillation circuit 21 and the external lighting control input 24, that is, the PWM oscillation circuit 21 always has an oscillation input, the external lighting control input 24. When the switching transistor 23 is switched, PWM control is performed to vary the pulse width of the on / off pulse of the supply voltage from the DC power supply unit 5 and is supplied to the LED 1 of the illumination unit 2 via the power cable W. Adjust the voltage.

  Based on the input of the external lighting control input 24, as shown in FIG. 2, for example, the low-luminance lighting of the LED 1 is performed by reducing the on-pulse width of a voltage of 12 V, and the high-luminance lighting is performed by increasing the on-pulse width. When the external lighting control input 24 is not input, the LED 1 is turned off.

  The information extraction means 7 in FIG. 1 includes a detection amplification unit 25 and a sampling circuit 26, and receives a communication signal including luminance information transmitted from the illumination unit 2 via the power cable W and superimposed on an on / off pulse of PWM control. , Taken out during PWM control off-pulse. The detection amplifying unit 25 includes, for example, a voltage comparator A1 and a resistor R1, and detects a current consumed during off-pulse of the illumination unit 2, that is, a communication signal transmitted from the transmission circuit 12 of the illumination unit 2 via the power cable W. Amplify.

  Based on the sampling from the PWM oscillation circuit 21, the sampling circuit 26 samples this communication signal at a sampling timing immediately before the on-pulse rising at the PWM control off-pulse. That is, the sampling frequency of the sampling circuit 26 is the same as the oscillation frequency of the PWM oscillation circuit 21. Since the drive current is lower when the LED is turned off than when the LED is turned on because the PWM control is turned off, the change in the current consumption of the illumination unit 2 can be detected stably. In addition, there are few noise components at the timing of switching of the PWM control, and the communication signal superimposed on the on / off pulse of the PWM control can be accurately taken out (restored). Further, since the communication signal is taken out immediately before the on-pulse rise in the PWM control off-pulse, a stable communication signal can be taken out with a simple circuit configuration and avoiding instability immediately after the on-pulse falls.

  As shown in FIG. 3, the DC power supply unit (constant voltage power supply) 5 has a voltage supplied to the illumination unit 2 at the time of PWM control on-pulse when the LED 1 of the illumination unit 2 is continuously lit and there is no off-pulse time. It is set to a voltage that can maintain a luminance equivalent to the average luminance. In other words, in the present invention, since the communication signal is extracted using the PWM control off-pulse, it is not possible to communicate with the continuous on-pulse as shown in FIG. is there. Moreover, as compared with the case where the average luminance is set by continuous on-pulse with a supply voltage of 12 V, the luminance is reduced by the presence of the off-pulse. Therefore, as shown in FIG. 3B, the supply voltage of the DC power supply unit 5 is slightly higher than 12V so that the same luminance as when the LED 1 is continuously lit can be maintained even when the PWM control off-pulse is present. Increased to 13V.

  The reception circuit 8 in FIG. 1 receives a communication signal including luminance information transmitted from the illumination unit 2 and detected and amplified. The correction circuit 9 corrects the luminance of the LED 1 based on the communication signal including the luminance information received and extracted by the information extracting means 7. The correction circuit 9 compares the communication signal with a pre-registered reference luminance. In response to this, a voltage obtained by correcting the on / off pulse width of the supply voltage is supplied to the illumination unit 2 via the power cable W, and the luminance of the LED 1 is automatically corrected. For example, when the brightness of the LED 1 is reduced, a voltage with a greatly varied on-pulse width of PWM control is supplied to the LED 1 so that the original brightness is maintained even if the brightness is increased by the brightness drop. To correct.

  The first drive power supply unit 10 includes a Zener diode Zd1, a switching transistor 27, and a resistor, and converts DC power from the DC power supply unit 5 into a predetermined value, for example, 5V. This voltage is supplied to the light receiving circuit 11 and the transmission circuit 12 of the illumination unit 2 via the power cable W when 12 V is not supplied during the PWM control on-pulse, that is, when the PWM control is off during the off-pulse.

  The voltage supplied to the illumination unit 2 at the time of PWM control off-pulse is set so that the light receiving circuit 11 and the transmission circuit 12 can be driven and the LED 1 is not lit. That is, as shown in FIG. 2, by outputting 12V at the time of the on-pulse of the PWM control for turning on the LED 1 and 5V at the time of the off-pulse for turning off the LED 1, a voltage of 12V or 5V is always supplied to the illumination unit 2, The supply voltage to the light receiving circuit 11 and the transmission circuit 12 is ensured.

  The illumination unit 2 in FIG. 1 includes a light receiving circuit 11, a transmission circuit 12, a signal generation circuit 13, and a second drive power supply unit 14 in addition to the plurality of LEDs 1 and the resistor R3. The light receiving circuit 11 detects the light projection state of the entire LED 1 or a part of the LED 1 as a received light amount like a PD (Photo Diode) (not shown) to obtain the luminance information. The transmission circuit 12 transmits a communication signal including at least luminance information of the LED 1 to the illumination driving unit 3 via the power cable W while being superimposed on an on / off pulse of PWM control.

  The signal generation circuit 13 includes a switching transistor 15 and a resistor R2, and the transmission circuit 12 transmits the signal based on a change in current consumption of the illumination unit 2 corresponding to luminance information obtained by the light receiving circuit 11. A communication signal including luminance information is generated. The current consumption of the illumination unit 2 refers to the load current consumed by the load of the entire illumination unit 2 during the PWM control off-pulse, and means the current consumption of the light receiving circuit 11 and the transmission circuit 12 during the PWM control off-pulse.

  The second drive power supply unit 14 includes a Zener diode Zd2, a switching transistor 16, a capacitor, and a resistor. As described above, a supply voltage of 12V is turned on from the DC power supply unit 5 through the power cable W, and a supply voltage of 5V is turned off. For example, the voltage is converted to a predetermined voltage of 3.3 V and supplied to the light receiving circuit 11 and the transmission circuit 12 to secure a supply voltage when the light is turned off.

  The communication means 4 includes a transmission circuit 12 and a signal generation circuit 13 provided in the illumination unit 2, a power cable W, and a reception circuit 8 provided in the illumination drive unit 3. The communication signal of the luminance information of the LED 1 generated by the signal generation circuit 13 is asynchronously communicated to the reception circuit 8 of the illumination driving unit 3 via the cable W without using the synchronization signal, such as an asynchronous communication signal. . As a result, the wiring of the synchronization signal cable can be omitted, and a simpler configuration is possible without increasing the number of cables for this purpose.

  An example of the operation of the LED lighting device having the above configuration will be described based on the time chart of FIG. 4 and the flowchart of FIG. First, a. As described above, a communication signal generated based on a change in current consumption (load current) corresponding to the luminance information of the LED 1 detected by the light receiving circuit 11 is transmitted from the transmission circuit 12. This communication signal is an asynchronous start-stop synchronization communication signal, which constitutes serial data. For example, binarized luminance information “00110000” follows the start bit, and a parity bit and a stop bit (not shown) are added. It becomes.

  In this example, as the luminance information included in the communication signal, the change in current consumption (load current) corresponding to the luminance information of the LED 1 is binarized (on / off). The size may be used as information indicating the intensity of luminance as it is.

  B. Of FIG. Is a. This communication signal is based on a change in current consumption (load current) of the illumination unit 2 corresponding to the luminance information of the LED 1. In FIG. The start bit of the communication signal and the “1” portion of the data are b. It corresponds to the part with large current consumption.

  On the other hand, c. As described above, an LED drive signal is output from the illumination drive unit 3 to the illumination unit 2 based on the external lighting control input 24. e. Indicates an on / off signal oscillated from the PWM oscillation circuit 21.

  D. Of FIG. As described above, in the illumination driving unit 3, a communication signal (current consumption) based on the luminance information transmitted from the illumination unit 2 is c. Is received and detected in a state of being superimposed on the LED drive signal on the illumination drive unit 3 side. F. Of FIG. Indicates a waveform obtained by sampling the state at the time of off-pulse of PWM control immediately before the on-pulse rises, that is, a communication signal extracted by the information extracting means 7. In this way, the communication signal is accurately extracted without being affected by the LED drive signal during the PWM control off-pulse.

The flowchart of FIG. 5 shows the operation of the luminance correction process of the illumination driving unit 3.
First, when a communication signal including luminance information based on a change in current consumption (load current) from the illumination unit 2 side is received by the reception circuit 8 of the illumination drive unit 3 (step S1), the communication signal (reception signal) Whether or not there is a start bit (step S2), and if there is no start bit, the process returns to step S1. If there is a start bit, the sampling circuit 26 samples the received signal when the PWM control is off, and the communication signal including the luminance information is accurately extracted and converted as received data (step S3).

  Next, a data error check and a luminance information averaging process in a predetermined period are performed in the receiving circuit 8 (step S4), and the correction circuit 9 compares the luminance information with the reference luminance to check whether it is bright. (Step S5). If it is brighter than the reference brightness, correction is performed to lower the output voltage by lowering the PWM control duty ratio (step S6). If it is darker than the reference brightness, the output voltage is raised or the duty of PWM control is reduced. Correction for increasing the LED driving current by increasing the ratio is performed (step S7). Thus, after the brightness of the LED 1 is corrected, the process returns to step S1.

  As described above, in the present invention, the communication signal including the luminance information of the LED 1 communicated by superimposing the PWM control on / off pulse from the illumination unit 2 to the illumination drive unit 3 via the power cable W is generated when the PWM control off pulse is transmitted. Since it is possible to extract the communication signal accurately without being affected by the current change that drives the LED as in the on-pulse when the LED is lit, without increasing the number of other cables. With a simple configuration, the communication signal can be superimposed on the on / off pulse of the PWM control so that it can be easily taken out.

It is a block diagram which shows the LED lighting apparatus which concerns on one Embodiment of this invention. It is a time chart which shows the illumination drive waveform of an LED illuminating device. It is a figure which shows a PWM control output. It is a time chart which shows operation | movement of the LED lighting apparatus of FIG. It is a flowchart which shows operation | movement of the LED lighting apparatus of FIG. (A) is a block diagram which shows the conventional LED lighting apparatus, (B) is a figure which shows a PWM control waveform. It is a block diagram which shows the LED lighting apparatus which has the conventional brightness correction circuit. (A) and (B) are block diagrams showing a conventional LED lighting device. It is a time chart which shows the intermittent drive of a LED lighting apparatus.

Explanation of symbols

1: LED
2: Illumination unit 3: Illumination drive unit 4: Communication unit 5: DC power supply unit 6: PWM control unit 7: Information extraction unit 8: Reception circuit 9: Correction circuit 10: First drive power supply 11: Light receiving circuit 12: Transmission circuit 13: Signal generation circuit 14: Second drive power supply C: Connector W: Power cable

Claims (4)

An illuminating unit having an LED, and the illuminating unit are connected by two power cables, and the voltage supplied to the illuminating unit is adjusted by PWM control that varies the on / off pulse width of the supply voltage from the DC power source unit. An LED illumination device comprising: an illumination drive unit that drives the LED to light up so that brightness can be adjusted; and a communication unit that communicates from the illumination unit to the illumination drive unit via the power cable,
The communication means performs communication by superimposing a communication signal including at least luminance information of the LED on an on / off pulse of the PWM control,
The said illumination drive part is an LED illuminating device provided with the information extraction means which takes out the communication signal containing the said communicated luminance information at the time of the OFF pulse of the said PWM control. In claim 1,
The illumination unit detects a light projection state of the entire LED or a part of the LED as a received light amount and obtains the luminance information, a transmission circuit that transmits a communication signal including the luminance information to the illumination driving unit, A signal generation circuit that generates a communication signal including the luminance information to be transmitted from the transmission circuit based on a change in current consumption of the illumination unit corresponding to the luminance information obtained by the light receiving circuit;
The illumination drive unit further receives a communication signal including the luminance information transmitted from the illumination unit, and a communication including the luminance information received by the reception circuit and extracted by the information extraction unit. An LED illumination device comprising: a correction circuit that corrects the brightness of the LED based on a signal. In claim 1,
Even if the voltage supplied to the illumination unit during the on-pulse of the PWM control is present during the off-pulse period of the PWM control, the luminance is equivalent to the average luminance when the LED of the illumination unit is continuously lit and there is no off-pulse time. LED lighting device set to a voltage capable of holding In claim 2,
The LED illumination device, wherein a voltage supplied to the illumination unit at the time of the PWM control off-pulse is set to a voltage at which the transmission circuit and the light receiving circuit can be driven and the LED is not lit.

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