JP5144445B2 - Dimming signal conversion circuit - Google Patents

Description

  The present invention relates to a dimming signal conversion circuit for supplying a DC voltage dimming signal for adjusting the brightness of a discharge lamp to a discharge lamp lighting circuit for lighting the discharge lamp.

For example, a discharge lamp lighting circuit used for a liquid crystal backlight has a dimming function for adjusting the brightness of the discharge lamp. In a system that uses a plurality of liquid crystal screens to increase the screen size, a plurality of discharge lamps and a plurality of discharge lamp lighting circuits for lighting the discharge lamps are provided. In this case, each discharge lamp lighting circuit is configured such that when each of the plurality of discharge lamps is lit, the light can be automatically adjusted so that each discharge lamp has uniform brightness. This type of technology is described in Patent Document 1, for example.
JP-A-8-213184

  In such a system that uses a plurality of liquid crystal screens to increase the screen size, when dimming with a DC voltage dimming signal, the DC voltage dimming signal is input to each discharge lamp lighting circuit corresponding to each liquid crystal screen. Since it is necessary, the wiring becomes long. Therefore, for example, a method in which a DC voltage dimming signal is input to the main discharge lamp lighting circuit and a DC voltage dimming signal from the main discharge lamp lighting circuit is transmitted to the other discharge lamp lighting circuits through a relay connector is conceivable. . However, in this case, when the DC voltage dimming signal is transmitted within the substrate of the discharge lamp lighting circuit, the DC voltage dimming signal is distorted due to the noise and the like output from the discharge lamp lighting circuit, thereby causing the discharge lamp to flicker, Or the phenomenon that the brightness of each discharge lamp differs may arise.

  An object of the present invention is to provide a dimming signal conversion circuit capable of reducing distortion of a DC voltage dimming signal supplied to a discharge lamp lighting circuit.

  The object is to provide a DC voltage dimming signal input unit for inputting a DC voltage dimming signal, and a first DC voltage dimming signal input from the DC voltage dimming signal input unit to convert the DC voltage dimming signal into a pulse width modulation signal. Conversion circuit, a pulse width modulation dimming signal input unit for inputting a pulse width modulation dimming signal from the outside, and a pulse width input from the first conversion circuit or the pulse width modulation dimming signal input unit A second conversion circuit for converting the modulation signal into a DC voltage dimming signal; and a pulse width modulation dimming signal output unit for outputting the pulse width modulation signal input to the second conversion circuit to the outside. This is achieved by a dimming signal conversion circuit.

  The discharge lamp lighting device according to the present invention includes the dimming signal conversion circuit and a discharge lamp lighting circuit that lights the discharge lamp based on a DC voltage dimming signal input from the dimming signal conversion circuit. . Here, a plurality of the discharge lamp lighting devices can be provided, and in this case, the pulse width modulation dimming signal output unit of the dimming signal conversion circuit of the discharge lamp lighting device has a dimming level of another adjacent discharge lamp lighting device. It is connected to the pulse width modulation dimming signal input section of the optical signal conversion circuit.

  ADVANTAGE OF THE INVENTION According to this invention, the light control signal conversion circuit which can reduce distortion of the DC voltage light control signal supplied to a discharge lamp lighting circuit can be obtained. As a result, even if a DC voltage dimming signal is input to one of the plurality of discharge lamp lighting devices and the dimming signal is transmitted from there to another discharge lamp lighting device using a relay connector or the like, distortion is not caused. A stable dimming signal with no or little distortion can be transmitted. In addition, the DC voltage dimming signal only needs to be input to one discharge lamp lighting device, and it is not necessary to input the DC voltage dimming signal to one or more other discharge lamp lighting devices. Wiring for transmission can be reduced.

  FIG. 1 is a diagram showing an embodiment of a dimming signal conversion circuit according to the present invention. The dimming signal conversion circuit 13 according to the present invention includes a DC voltage dimming signal input unit 51 for inputting a DC voltage dimming signal, and a DC voltage dimming signal 21 input from the DC voltage dimming signal input unit 51. Is converted into a pulse width modulation signal, a pulse width modulation dimming signal input unit 53 for inputting the pulse width modulation dimming signal 24 from the outside, and the first conversion circuit 52 or pulse width. A second conversion circuit 54 that converts the pulse width modulation signal input from the modulation dimming signal input unit 53 into a DC voltage dimming signal, and a pulse width modulation signal 26 input to the second conversion circuit 54 to the outside A pulse width modulation dimming signal output unit 55 for output. The first conversion circuit 52 includes a triangular wave generator 1, a comparator 2, a reference power supply 3, and a pull-up resistor 4. The second conversion circuit 54 includes a reference voltage 9, a pull-up resistor 10, a time constant setting resistor 11, and a time constant setting capacitor 12. Between the first conversion circuit 52 and the second conversion circuit 54, a diode 5 connected to the first conversion circuit 52, a diode 6 connected to the pulse width modulation dimming signal input unit 53, and a pull-down resistor 14. Comparator 7 with one input connected to diodes 5 and 6, and a reference voltage 8 connected to the other input of comparator 7.

  The triangular wave generator 1 of the first conversion circuit 52 outputs a triangular wave 22. The comparator 2 generates a pulse width modulation signal 23 by comparing the triangular wave with a DC signal that is the input DC voltage dimming signal 21. An example of a method for generating the pulse width modulation signal 23 will be described below with reference to FIG.

  As shown in FIG. 2, when the DC voltage dimming signal 21 is input to the plus side of the comparator 2 and the triangular wave 22 is input to the minus side of the comparator 2, the output from the comparator 2 becomes a pulse width modulation signal 23. In the pulse width modulation signal 23, the higher the DC voltage dimming signal 21, the wider the high level interval, and the lower the DC voltage dimming signal 21, the narrower the high level interval.

  The pulse width modulation signal 23, which is the output of the comparator 2, becomes the same voltage as the reference power supply 3 by the reference power supply 3 and the pull-up resistor 4. This pulse width modulation signal 23 is input to the plus side of the comparator 7 through the diode 5. A reference power supply 8 is input to the minus side of the comparator 7. The voltage of the reference power supply 8 is set to a voltage lower than the voltage of the reference power supply 3. The output signal of the comparator 7 is the same as the pulse width modulation signal 23 because the negative reference power supply 8 is lower than the high level of the pulse width modulation signal 23. The high level of this signal is equal to the voltage of the reference power supply 9 because the set voltage of the reference power supply 9 is transmitted through the pull-up resistor 10.

  The output signal of the comparator 7 is a signal having the same shape as the pulse width modulation signal 23, but is smoothed by the time constant setting resistor 11 and the time constant setting capacitor 12 and output as a DC voltage dimming signal 25. The signal output from the comparator 7 is output from the pulse width modulation dimming signal output unit 55 as the pulse width modulation dimming signal 26.

  In the dimming signal conversion circuit 13, when the pulse width modulation dimming signal 24 is input from the pulse width modulation dimming signal input unit 53, the DC voltage dimming signal 21 is not input from the DC voltage dimming signal input unit 51. At this time, only a low level signal is output from the comparator 2. On the other hand, the pulse width modulation dimming signal 24 inputted from the outside is inputted to the plus side of the comparator 7 through the diode 6. This signal is not affected by the signal from the comparator 2 because of the diode 5. Since the negative input of the comparator 7 is the reference power supply 8, the output of the comparator 7 is a signal having the same shape as the pulse width modulation dimming signal. This signal is smoothed by the time constant setting resistor 11 and the time constant setting capacitor 12 and output as a DC voltage dimming signal 25. The signal output from the comparator 7 is output from the pulse width modulation dimming signal output unit 55 as the pulse width modulation dimming signal 26.

  FIG. 3 is a diagram showing an embodiment of a discharge lamp lighting device according to the present invention. The present embodiment includes a plurality of discharge lamp lighting devices 30. Each discharge lamp lighting device 30 includes a dimming signal conversion circuit 13 and a discharge lamp lighting circuit 31 that lights the discharge lamp based on the DC voltage dimming signal input from the dimming signal conversion circuit. The pulse width modulation dimming signal output unit 55 of the dimming signal conversion circuit 13 in each discharge lamp lighting device 30 is a pulse width modulation dimming signal input unit of the dimming signal conversion circuit 13 in another adjacent discharge lamp lighting device 30. 53.

  When the DC voltage dimming signal 21 is input to the first-stage discharge lamp lighting device 30 in FIG. 3, the first-stage discharge lamp lighting device 30 receives the DC voltage dimming from the dimming signal conversion circuit 13. The signal 25 is output to the discharge lamp lighting circuit 31, and the pulse width modulation dimming signal 26 is output from the pulse width modulation dimming signal output unit 55 to the second stage discharge lamp lighting device 30. The second-stage discharge lamp lighting device 30 receives a DC voltage dimming signal from the dimming signal conversion circuit 13 based on the pulse width modulation dimming signal 24 input to the pulse width modulation dimming signal input unit 53. 25 is output to the discharge lamp lighting circuit 31, and the pulse width modulation dimming signal 26 is output from the pulse width modulation dimming signal output unit 55 to the third stage discharge lamp lighting device 30. Thereafter, the same operation as described above is repeated. Although the pulse width modulation dimming signal causes voltage distortion, the pulse width does not change. Therefore, even if the wiring becomes long, the pulse width can be accurately transmitted to another substrate.

  The present invention relates to a dimming signal conversion circuit for supplying a DC voltage dimming signal to a discharge lamp lighting circuit having a dimming function for adjusting the brightness of the discharge lamp, and has industrial applicability.

It is a figure which shows one Example of the light modulation signal conversion circuit which concerns on this invention. It is a figure for demonstrating an example of the production | generation method of a pulse width modulation signal. It is a figure which shows one Example of the discharge lamp lighting device which concerns on this invention.

Explanation of symbols

1 Triangular wave generator 2 Comparator 3, 8, 9 Reference power supply 4, 10 Pull-up resistor 5, 6 Diode 7 Comparator 11 Time constant setting resistor 12 Time constant setting capacitor 13 Dimming signal conversion circuit 14 Pull-down resistor 21, 25 DC Voltage dimming signal 22 Triangular wave 23, 24, 26 Pulse width modulation signal 51 DC voltage dimming signal input unit 52 First conversion circuit 53 Pulse width modulation dimming signal input unit 54 Second conversion circuit 55 Pulse width modulation dimming Signal output section

Claims (3)

  A DC voltage dimming signal input unit for inputting a DC voltage dimming signal, and a first conversion circuit for converting the DC voltage dimming signal input from the DC voltage dimming signal input unit into a pulse width modulation signal; A pulse width modulation dimming signal input unit for inputting a pulse width modulation dimming signal from the outside, and a pulse width modulation signal input from the first conversion circuit or the pulse width modulation dimming signal input unit as a direct current A second conversion circuit for converting to a voltage dimming signal and a pulse width modulation dimming signal output unit for outputting a pulse width modulation signal input to the second conversion circuit to the outside. A dimming signal conversion circuit.   A discharge lamp comprising: the dimming signal conversion circuit according to claim 1; and a discharge lamp lighting circuit that lights the discharge lamp based on a DC voltage dimming signal input from the dimming signal conversion circuit. Lighting device.   A pulse of a dimming signal conversion circuit of another discharge lamp lighting device, comprising a plurality of discharge lamp lighting devices according to claim 2, wherein the pulse width modulation dimming signal output unit of the dimming signal conversion circuit of the discharge lamp lighting device is adjacent. A discharge lamp lighting device connected to a width modulation dimming signal input unit.

Images