JPH07281631A - Method and circuit for driving dc discharging lamp - Google Patents

Abstract

PURPOSE:To prevent a variance in luminance in a video display device structured by regularly arranging DC discharging lamps (hereinafter called lamps) corresponding to pixels. CONSTITUTION:Constant current are discharged from lamps by transistors and these currents are set by means of outputs from a power comparison differential amplifier 21. Lamp voltages are calculated from the anode terminal potential of the lamp and a reference voltage by a lamp voltage calculation differential amplifier 41. A lamp voltage equivalent voltage and the current equivalent voltage of a current detector 13 are inputted to a multiplier 30 and a lamp input power equivalent voltage appears in its output. The power comparison differential amplifier 21, having calculated lamp power voltage and lamp power reference voltage as inputs, controls the lamp current with its output so that the values of input powers are kept constant with transistors, controls also lamp emitted light luminance at a constant value and limits a variance in luminance in a large type display device having a number of lamps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for a display DC discharge lamp, and more particularly to a driving method and a circuit for a display DC discharge lamp used as a pixel of a large image display device used outdoors.

[0002]

2. Description of the Related Art When one lamp is turned on in correspondence with one pixel and these lamps are regularly arranged to form an image display device, it is necessary to suppress a difference in brightness between the plurality of lamps, and the lamp emits light. By utilizing the discharge characteristic that the brightness is almost proportional to the lamp current and controlling the lamp current to be constant, the difference in brightness between a plurality of lamps is suppressed.

[0003]

However, in the conventional method of suppressing the brightness difference of the lamp by the constant current control, the manufacturing error,
If there is a difference in the lamp voltage during discharge due to temperature, etc., there will be a difference in the lamp input power between the multiple lamps even if they are driven at a constant current, and as a result, there will be variations in the emission brightness. There was the problem of letting it go.

[0004]

A method of driving a direct current discharge lamp according to the present invention is a direct current discharge in an image display device in which one direct current discharge lamp is arranged corresponding to one pixel and is illuminated with a constant current to display an image. In the method of driving a lamp, a step of detecting a lamp current for each DC discharge lamp, a step of detecting a lamp voltage for each DC discharge lamp, and a step of detecting lamp power in the form of a voltage from the lamp current and the lamp voltage. And a step of setting a reference voltage corresponding to a predetermined lamp power for each DC discharge lamp, and comparing the lamp power voltage detected for each DC discharge lamp with the reference voltage so that the lamp current is equalized. With controlling steps.

The reference voltage for each DC discharge lamp is a voltage corresponding to the lamp power for generating the brightness assigned to each DC discharge lamp.

Furthermore, the drive circuit of the DC discharge lamp of the present invention is a drive circuit of a DC discharge lamp in an image display device in which one DC discharge lamp is arranged corresponding to one pixel and is lit at a constant current to display an image. A discharge lamp unit having a DC discharge lamp, a lamp current detector of the DC discharge lamp, a lamp voltage detector and a control transistor, a voltage detected by the lamp voltage detector of the DC discharge lamp and a lamp voltage reference voltage source And a voltage calculation unit having a lamp voltage calculation differential amplifier and the lamp voltage reference voltage source, an output of the lamp voltage calculation differential amplifier, and a voltage detected by the lamp current detector as inputs. And a power for inputting the output of the multiplier and the lamp power reference voltage source and connecting the output to the base of the control transistor. Having a power control unit having a Kakusado amplifier and the lamp power reference voltage source, the power unit having a power supply discharge power supply and the amplifier.

The lamp current detector of the discharge lamp section may be a resistance shunt, and the lamp voltage detector may be a resistance voltage divider of the anode voltage of the discharge lamp.

The lamp voltage reference voltage source and the lamp power reference voltage source are also potentiometers connected to an amplifier power source, or a voltage divider composed of a fixed resistor and a variable resistor.

[0009]

The method and circuit for driving a DC discharge lamp according to the present invention comprises:
A DC discharge lamp, a lamp current detector for the lamp, and a control transistor for controlling the lamp current to an arbitrary constant value, and the voltage detected by the lamp voltage detector by the lamp voltage calculation differential amplifier and the lamp voltage reference voltage. The lamp voltage of the DC discharge lamp is calculated from the source, and the lamp power is output in the form of voltage by the multiplier having the lamp voltage and the voltage detected by the lamp current detector as input, and the power comparison differential amplifier is used. The output of the multiplier and the lamp power reference voltage source are input, and the output of the power comparison differential amplifier is connected to the base of the control transistor so that the voltage corresponding to the lamp power becomes equal to the lamp power reference voltage source. In addition, the lamp current is controlled to drive the DC discharge lamp.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. 1 is a block diagram of an embodiment of a drive circuit for a DC discharge lamp according to the present invention, and FIG. 2 is a slightly detailed circuit diagram of the drive circuit for the DC discharge lamp.

As shown in FIG. 1, the drive circuit of the DC discharge lamp has a discharge lamp section 1, a power control section 2, and a multiplication section 3.
And a voltage calculation unit 4 and a power supply unit 5.
Next, the configuration of each unit will be described with reference to FIG. The discharge unit 1 includes a DC discharge lamp 11 having a filament 101 as a cathode, a filament power supply 102 and an anode 103, a control transistor 12 and a lamp current detector 13.
And a lamp voltage detector 14, the voltage calculation unit 4 is composed of a lamp voltage reference voltage source 42 and a lamp voltage calculation differential amplifier 41, the multiplication unit 3 is composed of a multiplier 30, and the power control unit 2 is The lamp power reference voltage source 22 and the power comparison differential amplifier 21 are included, and the power supply unit 5 is configured with a discharging power supply 51 and an amplifier power supply 52.

Next, the operation of the drive circuit for the DC discharge lamp of the present invention will be described with reference to FIG. In the DC discharge lamp 11 of the discharge lamp unit 1, the filament 101 as a cathode is heated by the filament power supply 102, and electrons are easily emitted, and the discharge lamp power supply 51, the lamp current detector 13, and the control transistor 12 are provided. The constant current circuit configured by allows a constant lamp current to flow to turn on the DC discharge lamp 11. The collector current of the control transistor 12 is controlled by the output voltage of the power comparison differential amplifier 21, and when the output voltage of the power comparison differential amplifier 21 has a constant value, the lamp current is controlled to have a constant value.

The lamp voltage during discharge of the DC discharge lamp 11 is calculated by a lamp voltage reference voltage source 42 and a voltage obtained by appropriately dividing the potential of the anode terminal of the DC discharge lamp 11 by the lamp voltage detector 14. Differential amplifier 4
It is calculated by 1 and output to the multiplier 30.

The output voltage of the differential amplifier 41 for lamp voltage calculation and the lamp current of the DC discharge lamp 11 by the lamp current detector 13 are input to the multiplier 30 as voltage values in the multiplier 30, and the DC discharge lamp 11 is supplied. The voltage proportional to the electric power of is output from the multiplier 30.

The power comparison differential amplifier 21 includes a multiplier 30.
The output voltage proportional to the lamp power and the lamp power reference voltage source 22 are input, the difference is calculated, and the collector current of the control transistor 12 is controlled by the calculation result.

The output of the power comparison differential amplifier 21 operates so that the voltage of the lamp power reference voltage source 22 and the output voltage of the multiplier 30 become equal, and as a result, the lamp current flowing into the DC discharge lamp 11 is The DC discharge lamp 1 has a power value indicated by the lamp power reference voltage source 22 with respect to the voltage.
The input power of 1 is controlled to be equal, and the input power of the DC discharge lamp 11 is controlled to a constant value.

The lamp power reference voltage source 22 can indirectly control the input current of the DC discharge lamp 11 according to its voltage value. By setting the lamp power reference voltage source 22 to an arbitrary value, the input of the DC discharge lamp 11 can be controlled. The power can be controlled arbitrarily.

[0018]

As described above, the method and circuit for driving a DC discharge lamp according to the present invention has a mechanism for detecting the lamp power and controlling the lamp current so that it becomes the same value as the reference power. Even under such conditions, the amount of power flowing into the DC discharge lamp can be controlled to be constant, and the emission brightness can be controlled to the reference brightness for the DC discharge lamp that emits light with a brightness proportional to the amount of power flowing in. In a display device in which a plurality of lamps are arranged, it is possible to form a high-quality display screen without variations in brightness.

Further, it is possible to correct the change in the emission brightness of the DC discharge lamp due to the change over time of the DC discharge lamp, and the deterioration of the image quality due to the change in the brightness due to the change over time can be corrected. There is an effect that can be prevented.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an embodiment of a drive circuit for a DC discharge lamp of the present invention.

FIG. 2 is a slightly detailed circuit configuration diagram of an embodiment of the drive circuit for the DC discharge lamp.

[Explanation of symbols]

 1 Discharge Lamp Section 2 Power Control Section 3 Multiplying Section 4 Voltage Calculation Section 5 Power Supply Section 11 DC Discharge Lamp 12 Control Transistor 13 Lamp Current Detector 14 Lamp Voltage Detector 21 Power Comparison Differential Amplifier 22 Lamp Power Reference Voltage Source 30 Multiplier 41 Lamp Voltage Calculation Differential Amplifier 42 Lamp Voltage Reference Voltage Source 51 Discharge Power Supply 52 Amplifier Power Supply 101 Filament 102 Filament Power Supply 103 Anode

Claims (5)

[Claims] 1. A method for driving a DC discharge lamp in an image display device, wherein one DC discharge lamp is arranged corresponding to one pixel and is lit at a constant current to display an image. A lamp current is detected for each DC discharge lamp. The step of detecting the lamp voltage for each DC discharge lamp, the step of detecting the lamp power in the form of voltage from the lamp current and the lamp voltage, and the reference corresponding to the predetermined lamp power for each DC discharge lamp. Driving a DC discharge lamp, comprising the steps of setting a voltage and controlling the lamp current so that the lamp power voltage detected for each DC discharge lamp and a reference voltage are compared and made equal. Method. 2. The method of driving a DC discharge lamp according to claim 1, wherein the reference voltage for each DC discharge lamp is a voltage corresponding to the lamp power for generating the brightness assigned to each DC discharge lamp. 3. A drive circuit for a DC discharge lamp in an image display device in which one DC discharge lamp is arranged corresponding to one pixel and is illuminated with a constant current to display an image. A discharge lamp unit having a lamp current detector, a lamp voltage detector, and a control transistor; and a lamp voltage calculation differential inputting the voltage detected by the lamp voltage detector of the DC discharge lamp and a lamp voltage reference voltage source. A voltage calculation unit having an amplifier and the lamp voltage reference voltage source; a multiplication unit having a multiplier that receives the output of the ramp voltage calculation differential amplifier and the voltage detected by the lamp current detector as inputs; Comparator and a lamp power reference voltage for connecting the output to the base of the control transistor with the output of the power supply and the lamp power reference voltage source as inputs Driving circuit for a DC discharge lamp, characterized in that it comprises a power control unit, a power supply unit having a power supply discharge power supply and the amplifier having a. 4. The drive circuit for a DC discharge lamp according to claim 2, wherein the lamp current detector of the discharge lamp unit is a resistance shunt, and the lamp voltage detector is a resistance voltage divider of an anode voltage of the discharge lamp. 5. The driving of a DC discharge lamp according to claim 2, wherein the lamp voltage reference voltage source and the lamp power reference voltage source are potentiometers connected to an amplifier power supply or voltage dividers composed of fixed resistors and variable resistors. circuit.