JP6563315B2 - LED controller - Google Patents

Description

  The present invention relates to an LED control device that controls the lighting state of an LED.

  As a method for controlling the lighting state of the LED, PWM dimming performed by changing the duty ratio of the PWM signal is widely used (for example, Patent Document 1). FIG. 3 shows a configuration of a main part of a conventional LED control device. In this LED control device, a control device 20A is connected to a system circuit 10A that controls an LED (not shown) using a single cable 30A. The control device 20A is equipped with a power supply of voltage VDD and supplies power to the operation unit 21. A signal indicating the operation content in the operation unit 21 generates a voltage Vc at the resistor R1 of the system circuit 10A via the single-wire cable 30A, and this voltage Vc is converted from an analog signal to a digital signal by the AD converter 11, and converted. A value (setting signal) is input to an LED control unit (not shown), a duty ratio of a PWM signal for dimming control of the LED is set, or lighting / extinguishing of the LED is controlled.

  FIG. 4 shows a configuration of a main part of another conventional LED control device. In this LED control device, the control device 20B is connected to the system circuit 10A using two cables 30 including cables 31 and 32. The control device 20B is supplied with power from the internal power supply voltage VDD of the system circuit 10A via the cable 31. The control device 20B is equipped with a variable resistor R5. The signal in which the resistance value of the variable resistor R5 is adjusted generates a voltage Vc at the resistor R1 of the system circuit 10A via the cable 32. This voltage Vc is converted from an analog signal to a digital signal by the AD converter 11, and the converted value is obtained. (Setting signal) is input to an LED control unit (not shown), a duty ratio of a PWM signal for dimming control of the LED is set, or lighting / extinguishing of the LED is controlled.

Japanese Patent Application No. 2012-164746

  However, the LED control device described with reference to FIG. 3 has the advantage that only one cable 30A is required, but it is necessary to equip the control device 20A with a power supply of the voltage VDD. Is required specially. If the control voltage Vc to the system circuit 10A includes noise, the conversion value output from the AD converter 11 may fluctuate, and the LED may not be accurately controlled.

  In addition, the LED control device described with reference to FIG. 4 has an advantage that it is not necessary to equip the control device 20B with a power supply. However, if noise is included in the control voltage Vc to the system circuit 10A, it is output from the AD converter 11. There are cases where the conversion value fluctuates and the LED cannot be accurately controlled, as in the LED control device described with reference to FIG.

  An object of the present invention is to provide an LED control device that is strong against noise and that can realize multiple commands.

  In order to achieve the above object, an LED control device according to a first aspect of the present invention is an LED control device that sets a brightness of the LED by outputting a PWM signal with a predetermined duty to the LED. A command for determining the duty is output based on a determination result obtained by comparing a first resistance for pressure and a setting signal corresponding to a control voltage generated in the first resistance with a plurality of comparison reference values. A system circuit having a comparison means; and a control device having a resistance switching means; and connecting an output side of the resistance switching means of the control device to the first resistance of the system circuit, When the setting signal corresponding to the control voltage generated in the resistor is collated with the plurality of comparison reference values, each of the plurality of comparison reference values has a predetermined range. And butterflies.

  According to a second aspect of the present invention, in the LED control device according to the first aspect, the system circuit is obtained by a resistance value set by the resistance switching unit of the control device and a resistance value of the first resistor. The setting signal is generated in response to a control voltage obtained by dividing the voltage of the internal power supply.

  According to a third aspect of the present invention, in the LED control device according to the first or second aspect, the comparing means of the system circuit issues a command for maintaining the current state of the duty when the setting signal is a first value. A command to increase the duty by one step when the setting signal is a second value, a command to decrease the duty by one step when the setting signal is a third value, and a setting signal that has a fourth value A command for setting the duty to a first specific value, and a command for setting the duty to a second specific value when the setting signal is a fifth value, respectively, as a determination result. .

  According to a fourth aspect of the present invention, in the LED control device according to the third aspect, the system circuit includes a counter, and the counter is a count value when the determination result of the comparing means is a command to increase by one step. Is incremented by 1, and when the determination result of the comparing means is a command to decrease by 1 step, the count value is decremented by 1 so that the count value of the counter becomes the duty of the PWM signal. Features.

  The invention according to claim 5 is the LED control device according to claim 3 or 4, wherein the first resistor of the system circuit is a fixed resistor, and the resistance switching means of the control device is a fixed resistor. 2 and a third and fourth resistors that are variable resistors, and the setting signal becomes the first value by selecting the second resistor in the resistance switching means of the control device. In the resistance switching unit of the control device, the second and third resistors are selected and the third resistor is adjusted to a first resistance value, so that the setting signal is changed to the first resistance value. The setting signal is switched to the third value by selecting the fourth resistance and adjusting it to the third resistance value in the resistance switching means of the control device. In the resistance switching means of the control device, the setting signal is selected by selecting the second resistance and the fourth resistance and adjusting the fourth resistance to a fourth resistance value. Is switched to be the fourth value, and the resistance switching means of the control device selects the fourth resistor and adjusts it to the fifth resistance value, so that the setting signal becomes the fifth value. It is possible to switch to a value of.

  According to the present invention, since each of the plurality of comparison reference values has a predetermined range, it is possible to prevent an erroneous determination from being made even if a fluctuation or noise occurs in the control voltage generated by the operation of the control device. That is, the noise tolerance is increased.

  Also, by dividing and using the voltage range of the internal power supply, the number of types of setting signals can be increased. Therefore, in addition to the normal PWM signal dimming control for LEDs that increase or decrease the duty In addition, it is possible to perform a special operation of turning off the LED, setting the maximum brightness, or setting another specific brightness.

It is a block diagram of the principal part of the LED control apparatus of the Example of this invention. It is explanatory drawing of the control content of the LED control apparatus of the Example of this invention. It is a block diagram of the principal part of the conventional LED control apparatus. It is a block diagram of the principal part of another conventional LED control apparatus.

  FIG. 1 shows a configuration of a main part of an LED control device according to one embodiment of the present invention. Reference numeral 10 denotes a system circuit, 20 denotes a control device, and 30 denotes a two-wire cable connecting the system circuit 10 and the control device 20.

  The system circuit 10 includes a fixed resistor R1 that generates a control voltage Vc, an AD converter 11 that converts the control voltage Vc from an analog signal into a digital setting signal having a predetermined number of bits, and a plurality of comparison references having a predetermined range. The memory 12 storing the value and the setting signal output from the AD converter 11 are checked against a plurality of comparison reference values stored in the memory 12, and the comparator 13 outputs the converted value or command as the determination result. And a counter 14 that counts and outputs a final converted value when the determination result of the comparator 13 is a converted value.

  The control device 20 includes one-input two-output switches S1 and S2, a variable resistor R3 connected to the contact b of the switch S1, a fixed resistor R2 connected to the contact a of the switch S2, and a contact b of the switch S2. And a variable resistor R4 connected to the. The resistance value of the resistor R2 is the same as the resistance value of the resistor R1.

  The two-wire cable 30 includes a cable 31 for supplying the power supply of the voltage VDD in the system circuit 10 to the contact c of the switches S1 and S2 of the control device 20, the non-grounded side of the resistor R1 of the system circuit 10, and the control device 20 And a cable 32 connecting the common connection points of the resistors R2, R3, and R4.

  As the plurality of comparison reference values stored in the memory 12 of the system circuit 10, data corresponding to five types of 0, 0.25 VDD, 0.5 VDD, 0.75 VDD, and VDD are used when the power supply voltage is VDD. To do. The comparator 13 determines by collation which of the five types of comparison reference values the setting signal output from the AD converter 11 corresponding to the control voltage Vc corresponds to.

  FIG. 2 shows the control contents. (1) When the switches S1 and S2 are respectively switched to the contact point a, the voltage VDD of the internal power supply is divided by the resistors R1 and R2, and the control voltage Vc is set to 0.5 VDD. The setting signal corresponding to the voltage Vc is collated with a plurality of comparison reference values stored in the memory 12 in the comparator 13 and corresponds to the comparison reference value corresponding to 0.5 VDD. The current status will be maintained. That is, neither the command nor the conversion value changes from the current state, and the duty of the PWM signal is in a normal state where it does not change. As described above, the switches S1 and S2 are normally switched to the contact a.

  (2) When the switch S1 is switched to the contact b, the switch S2 is switched to the contact a, and the value of the variable resistor R3 is set to 0.5R2, the voltage VDD of the internal power supply of the system circuit 10 is changed between the resistor R3 and the resistor R3. The control voltage Vc is set to 0.75 VDD by dividing by the parallel connection resistance value of R2 and the resistance R1. The setting signal corresponding to the voltage Vc is collated with a plurality of comparison reference values stored in the memory 12 in the comparator 13 and corresponds to the comparison reference value corresponding to 0.75 VDD. It will be up. At this time, the counter 14 is incremented by 1, and the conversion value is incremented by 1%. Thereby, for example, when the duty of the current PWM signal is 80%, the duty is increased to 81%.

  After that, when the switch S1 is returned to the contact a while the switch S2 is switched to the contact a, the state returns to the state (1) and the control voltage Vc becomes 0.5 VDD. Is switched to the contact b, the control voltage Vc is set to 0.75 VDD again. For this reason, the “determination result” is increased again, and the duty of the PWM signal is further increased by 1% from 81% to 82%. Thereafter, by repeating the same operation, the conversion value is increased by 1 and the duty of the PWM signal is increased by 1%.

  (3) When the switch S1 is switched to the contact a, the switch S2 is switched to the contact b, and the value of the variable resistor R4 is set to the value 3R1, the voltage VDD of the internal power supply of the system circuit 10 is changed by the resistor R4 and the resistor R1. The voltage is divided to set the control voltage Vc to 0.25 VDD. The setting signal corresponding to the voltage Vc is compared with a plurality of reference values stored in the memory 12 in the comparator 13 and corresponds to the comparison reference value corresponding to 0.25 VDD, so that the “judgment result” is reduced. It becomes. At this time, the counter 14 is counted down by 1, and the conversion value is decreased by 1%. Thereby, for example, when the duty of the current PWM signal is 80%, the duty is reduced to 79%.

  Thereafter, when the switch S2 is returned to the contact a while the switch S1 is switched to the contact a, the state returns to the state (1) and the control voltage Vc becomes 0.5 VDD. Is switched to the contact b, the control voltage Vc is set to 0.25 VDD again. For this reason, the “determination result” is again decreased, and the duty of the PWM signal is decreased by 1% from 79% to 78%. Thereafter, by repeating the same operation, the conversion value is decreased by 1 and the duty of the PWM signal is decreased by 1%.

  (4) When the switch S1 is switched to the contact b and the switch S2 is switched to the contact a, and the resistance value of the variable resistor R3 is set to 0, the voltage VDD of the internal power supply of the system circuit 10 is directly applied to the resistor R1. Thus, the control voltage Vc is set to VDD. The setting signal corresponding to the voltage Vc is compared with a plurality of reference values stored in the memory 12 in the comparator 13 and corresponds to the comparison reference value corresponding to VDD. Become. At this time, for example, if a command for setting the duty of the PWM signal to 100% is given to the command 1, whatever the value of the duty of the current PWM signal is, the duty immediately becomes 100%. The LED has the maximum brightness.

  Thereafter, for example, when the switch S1 is switched to the contact point a, the switch S2 is switched to the contact point b, and the resistance value of the variable resistor R4 is switched to 3R1, the voltage Vc becomes 0. Set to 25 VDD. Therefore, the “determination result” is down, and the PMW duty is reduced by 1% from 100% to 99%.

  (5) When the switch S1 is switched to the contact a and the switch S2 is switched to the contact b, and the resistance value of the variable resistor R4 is set to the maximum value (for example, ∞, R4 >> R1), the voltage of the internal power supply of the system circuit 10 VDD is directly applied to the resistor R4, and the control voltage Vc is set to zero. The setting signal corresponding to the voltage Vc is compared with a plurality of reference values stored in the memory 12 in the comparator 13 and corresponds to the comparison reference value corresponding to 0, so that the “determination result” is the command 2 Become. In this case, for example, if a command for setting the duty of the PWM signal to 0% is given to the command 2, whatever the value of the duty of the current PWM signal is immediately 0% The LED is turned off.

  Then, for example, when the switch S1 is switched to the contact b, the switch S2 is switched to the contact a, and the resistance value of the variable resistor R3 is switched to 0.5R2, the voltage Vc is changed as shown in (2) above. Set to 0.75 VDD. For this reason, the “determination” of the comparator 13 is up, and the duty of the PMW is increased from 0% to 1%.

  In the example described above, the comparison reference value when the “determination result” is up is set to a value in a range including a value corresponding to 0.75 VDD. The comparison reference value is 0.5VDD <Vc. Any one of the ranges of <VDD may be supported. In the example described above, the comparison reference value when the “judgment result” is down is a value in a range including a value corresponding to 0.25VDD. The comparison reference value is 0 <Vc <0. Any one of the ranges of .5VDD may be supported.

  Furthermore, up and down may be reversed. That is, when the comparison reference value when the “judgment result” is down is set to a value in a range including a value corresponding to one of the ranges of 0.5VDD <Vc <VDD, and the “judgment result” is up The comparison reference value may be set to a value in a range including a value corresponding to one of the ranges of 0 <Vc <0.5VDD.

  Further, in the above description, the command is two commands, ie, the command 1 with the voltage Vc of VDD and the command 2 with the voltage Vc of 0, but the resistance values of the variable resistors R3 and R4 of the control device 20 are appropriately set to values different from the above values. By setting, it does not overlap any of the above-mentioned up (= 0.75 VDD), down (= 0.25 VDD), current status maintenance (= 0.5 VDD), command 1 (= VDD), command 2 (= 0) If the control voltage Vc is obtained in the voltage range, three or more commands can be set. As a result, for example, a plurality of arbitrary luminances can be set in addition to turning off and maximum luminance.

  According to the LED control device of the present embodiment, since the voltage VDD of the internal power supply of the system circuit 10 is supplied to the control device 20 using the two-wire cable 30, no internal power supply is required for the control device 20. Thus, the circuit scale of the control device 20 can be reduced. Note that the control device 20 may include an internal power supply.

  Further, since the plurality of comparison reference values stored in the memory 12 each have a predetermined range, if the setting signal corresponding to the control voltage Vc is included in the range of the comparison reference value, a corresponding determination result can be output. Even if a fluctuation or noise occurs in the control voltage Vc generated by the operation of the control device 20, it is possible to prevent erroneous determination. That is, the noise tolerance is increased.

  Furthermore, since the range of the voltage VDD of the internal power supply is divided into a plurality and used, the types of setting signals can be increased, so that the normal PWM dimming control of the LED that increases or decreases the duty can be performed. In addition, it is possible to perform a special operation for turning off the LED, setting the maximum brightness, or setting another specific brightness.

10, 10A: System circuit, 11: AD converter, 12: Memory, 13: Comparator, 14: Counter 20, 20A, 20B: Control device, 21: Operation unit 30: Two-wire cable, 30A: Single wire cable, 31, 32: Cable

Claims (5)

In an LED control device for setting a luminance of the LED by outputting a PWM signal having a predetermined duty to the LED,
For determining the duty based on a determination result obtained by comparing a setting signal corresponding to an internal power source, a first resistor for voltage division, and a control voltage generated in the first resistor with a plurality of comparison reference values A system circuit having comparison means for outputting a command;
A control device comprising a resistance switching means,
An output side of the resistance switching unit of the control device is connected to the first resistor of the system circuit, and the setting signal corresponding to the control voltage generated in the first resistor is connected to the plurality of comparison reference values. When matching
The plurality of comparison reference values each have a predetermined range. The LED control device according to claim 1,
The system circuit corresponds to the control voltage obtained by dividing the voltage of the internal power source obtained by the resistance value set by the resistance switching unit of the control device and the resistance value of the first resistor. An LED control device that generates a signal. The LED control device according to claim 1 or 2,
The comparing means of the system circuit provides a command for maintaining the current state of the duty when the setting signal is a first value, and a command for increasing the duty by one step when the setting signal is a second value, When the setting signal is a third value, a command to decrease the duty by one step, when the setting signal is a fourth value, a command to set the duty to the first specific value, the setting signal is the fifth An LED control device that outputs a command to set the duty to a second specific value as a determination result when the value is The LED control device according to claim 3,
The system circuit includes a counter, and the counter increments the count value by 1 when the determination result of the comparison unit is an instruction to increase by one step, and the determination result of the comparison unit decreases by the one step. The LED control device according to claim 1, wherein the count value is counted down by 1 when the command is issued, and the count value of the counter becomes the duty of the PWM signal. The LED control device according to claim 3 or 4,
The first resistor of the system circuit is a fixed resistor, and the resistance switching means of the control device includes a second resistor that is a fixed resistor, and third and fourth resistors that are variable resistors,
In the resistance switching means of the control device, the setting signal is switched to be the first value by selecting the second resistance,
In the resistance switching means of the control device, the setting signal becomes the second value by selecting the second and third resistors and adjusting the third resistance to the first resistance value. Switched to
In the resistance switching means of the control device, the setting signal is switched to become the third value by selecting the fourth resistance and adjusting to the third resistance value,
In the resistance switching means of the control device, the setting signal is set to the fourth value by selecting the second resistance and the fourth resistance and adjusting the fourth resistance to a fourth resistance value. Switched to be
In the resistance switching means of the control device, the setting signal is switched to become the fifth value by selecting the fourth resistance and adjusting it to the fifth resistance value.
An LED control device.

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