KR0138675B1 - Brightness control circuit of a monitor - Google Patents

Abstract

The present invention relates to a brightness control circuit of a monitor that can be controlled in a more precise and various steps by controlling the brightness in a digital manner using a pulse width modulation signal output from the microprocessor.

To this end, in a brightness control circuit of a monitor in which a predetermined voltage generated by a flyback transformer is extracted by a first negative power output circuit and applied to a cathode ray tube grid terminal, the monitor system is controlled and the brightness data is pulse width. A microprocessor outputting a modulated signal, a F / V converter outputting a stable voltage in proportion thereto using a pulse width modulation signal output from the microprocessor, and a voltage proportional to the output level of the F / V converter A voltage limiting circuit for restrictive output and a output circuit of the voltage limiting circuit. A plurality of resistors are connected in series and in series to synthesize and distribute the output voltages of the voltage limiting circuit and the flyback transformer to apply to the cathode tube and the grid terminal. It consists of.

Description

Monitor Brightness Control Circuit

1 is a brightness control circuit diagram of a conventional monitor.

2 is a brightness control circuit diagram of a monitor according to the present invention.

3 is a detailed circuit diagram of components in accordance with the present invention.

4 is an input / output voltage table in each stage according to the present invention.

* Explanation of symbols for main parts of the drawings

1: blanking pulse generating unit 2: DC blocking unit

3: second negative power output circuit 4: power supply

5: Flyback transformer 6: first negative power output circuit

8: Voltage limiting circuit 9: F / V converter

9a: comparator 9b: ripple cancellation circuit

10 microprocessor 11: distribution circuit

Q: Transistors R1 to R10: Resistance

D1 to D2: Diodes C1 to C3: Capacitor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brightness control circuit of a monitor, and in particular, to control brightness in a digital manner by using a pulse width modulation (PWM) signal output from a microprocessor, so that the brightness of a monitor can be adjusted in more precise and various steps. It is about control circuit

In general, the brightness control device for the monitor, according to the user's selection is to adjust the brightness by controlling the grid voltage of the cathode ray tube by adjusting the volume installed outside the monitor.

That is, FIG. 1 is a brightness control circuit diagram of a conventional monitor. The first negative power output circuit 6 is connected to an output terminal of a flyback transformer 5 that generates a predetermined level of power at power-on and outputs only negative power. 1 is connected to the output terminal of the negative power output circuit (6) and consists of a variable resistor (VR) and a plurality of resistors (R1 to R3) to change the output level of the flyback transformer (5) applied to the cathode ray tube grid terminal (G1) A second negative power output circuit 3 which is connected in parallel to the brightness adjusting unit 7 for adjusting the brightness, and outputs only the negative power using the power output from the power supply device 4 in parallel with the output terminal of the brightness adjusting unit 7, The DC blocking unit 2 is connected in parallel to the output terminal of the brightness control unit 7 to block the DC included in the blanking signal output from the blanking pulse generator 1.

In the brightness control circuit of the monitor including such a peripheral circuit, first, a voltage of a predetermined level output from the power supply device 4 is a second negative sound consisting of a condenser C1, a diode D1, and a resistor R4. A negative power of an appropriate level is output by the power supply output circuit 3 and applied to the cathode ray tube grid terminal G1.

In addition, the blanking pulse according to the operating frequency of each mode of the monitor is output from the blanking pulse generator 1, and the blanking pulse passes through the DC blocking unit 2 to remove the DC component included in the blanking pulse, thereby reducing the cathode ray tube grid terminal. A voltage of a predetermined level is supplied to G1.

On the other hand, the voltage of the predetermined level output from the flyback transformer 5 outputs the negative power of the appropriate level through the first negative power output circuit 6 composed of the diode D2 and the capacitor C2. This negative power source is applied to the cathode ray tube grid terminal G1 via the brightness adjusting unit 7.

Therefore, the negative potential of about -45V to -75V is supplied to the grid terminal G1 of the cathode ray tube by the voltage output from the power supply device 4, the blanking pulse generator 1, and the flyback transformer 5. The brightness of the monitor is changed according to the voltage level of the negative potential applied to the grid terminal G1.

That is, the output voltage of the flyback transformer 5 applied to the cathode ray tube grid terminal G1 according to the adjustment of the variable resistor VR of the brightness controller 7 is divided by the variable resistor VR and the resistors R1 to R3. This causes the negative power output level to vary between -45V and -75V, resulting in a change in brightness of the monitor.

Such brightness control circuit of the conventional monitor controls the brightness by an analog method of changing the negative power applied to the cathode ray tube grid terminal by adjusting the variable resistor, but the brightness by digital control by the limitation of the adjustment step and the control of the microprocessor. There is a problem that can not be controlled.

SUMMARY OF THE INVENTION The present invention provides a brightness control circuit for a monitor that contributes to improving the reliability of a monitor by controlling the screen brightness of a monitor in a digital manner to precisely adjust the brightness of a screen in order to solve the above problems. Is there.

In order to achieve the above object, the present invention relates to a brightness control circuit of a monitor in which a predetermined voltage generated by a flyback transformer is extracted by a first negative power output circuit and applied to a cathode ray tube grid terminal. A microprocessor that controls the system and outputs brightness data as a pulse width modulated signal, an F / V converter that outputs a stable voltage in proportion to the pulse width modulated signal output from the microprocessor, and the F / V converter A voltage limiting circuit for restrictively outputting a voltage proportional to the output level, and is connected to an output terminal of the voltage limiting circuit, and a plurality of resistors are connected in parallel to synthesize and distribute the output voltages of the voltage limiting circuit and the flyback transformer. It is composed of a distribution circuit applied to the cathode ray tube grid terminal.

Hereinafter, described in detail by the accompanying drawings as follows.

2 is a brightness control circuit diagram of the monitor according to the present invention, the output terminal of the blanking pulse generator 1 is connected to the cathode ray tube grid terminal (G1) through the DC blocking unit (2), the power supply device (4) The output terminal is connected in parallel to the cathode ray tube grid terminal G1 via the second negative power output circuit 3.

In addition, the output side of the flyback transformer (5) is connected to one end of the distribution circuit (11) via a first negative power output circuit (6), and an F / V converter (9) on one output terminal of the microprocessor (10). Connected to the voltage limiting circuit (8), and on the output side of the voltage limiting circuit (8), the output voltage of the flyback transformer (5) and the output of the voltage limiting circuit (8) are synthesized and distributed to form a cathode ray tube grid terminal. It is connected to the other end of the distribution circuit 11 supplied to (G1).

FIG. 3A is a detailed circuit diagram of the F / V converter 9 in which noise included in the pulse width modulated signal output from the microprocessor 10 by the resistor R7 and the capacitor C4 is removed. A comparator 9a for comparing the signal with the reference voltage Vref set by the resistors R5 and R6 and outputting a pulse signal as a voltage, and connected between an output terminal of the comparator 9a and an inverting terminal (-), The resistor R7 and the capacitor C3 are connected in parallel to each other and constitute a ripple removing unit 9b for removing the ripple component included in the output voltage of the comparator 9a.

FIG. 3B is a voltage limiting circuit diagram of a transistor Q connected to an output side of the F / V converter 9 and outputting a voltage proportionally to the distribution circuit 11 according to an input level. It is composed of resistors R8 to R10 connected to each end of Q) and connected in parallel to the power supply terminal 12V to limit the output voltage of the transistor Q.

According to the present invention, the voltage of the predetermined level output from the power supply device 4 is first appropriated by the second negative power output circuit 3 composed of the capacitor C1, the diode D1, and the resistor R4. The negative power of the level is output and applied to the cathode ray tube grid terminal G1.

In addition, the blanking pulse according to the operating frequency of each mode of the monitor is output from the blanking pulse generator 1, and the blanking pulse passes through the DC blocking unit 2 to remove the DC component included in the blanking pulse, thereby reducing the cathode ray tube grid terminal. A voltage of a predetermined level is supplied to G1.

The voltage of a predetermined level output from the flyback transformer 5 outputs a negative power of an appropriate level through the first negative power output circuit 6 composed of a diode D2 and a capacitor C2. This negative power source is applied to the cathode ray tube grid terminal G1 via the brightness adjusting unit 7.

On the other hand, when the user inputs the brightness data of the monitor by operating a keyboard or tact switch not shown to adjust the screen brightness of the monitor, the microprocessor 10 recognizes that the brightness adjustment mode of the monitor is proportional to the amount of manipulation of the keyboard or tact. The pulse width modulated signal is output.

Therefore, the pulse width modulated signal output from the microprocessor 10 removes noise by the capacitor C4 and the resistor R7 of the F / V converter 9 and then the inverting terminal (-) of the comparator 9a. Is applied to.

At this time, the power of 12V is divided by the resistors R5 and R6, and the divided voltage is applied to the non-inverting terminal + of the comparator 9a as the reference voltage Vref, so that the comparator 9a is input. The reference voltage Vref and the pulse width modulated signal output from the microprocessor 10 are compared with each other to output a voltage having a predetermined level in a range in which the pulse width modulated signal is higher than the reference voltage Vref.

That is, as shown in FIG. 4, when the pulse width modulated signal output from the microprocessor 10 is changed from 0V to 3.46V, the output voltage of the F / V converter 9 is within the range of 5.27V to 10.7V. The output is changed proportionally.

In addition, the output voltage of the F / V converter 9 is applied as a bias voltage of the transistor Q which is the voltage limiting circuit 8, and the output voltage of the transistor Q changes according to this bias voltage level.

That is, although the base of the transistor Q1 and the former positions of the emitters set by the resistors R8 and R9 are set, the base and the emitter of the transistor Q are changed in accordance with the increase or decrease of the output voltage of the F / V converter 9. As the potential difference between the terminals changes, the output level of the transistor Q eventually changes, and when the output of the F / V converter 9 changes from 10.7V to 5.27V as shown in FIG. 4, the output of the voltage limiting circuit 8 becomes The change is in the range of -56.9V to 0.38V.

Therefore, the output voltage of the voltage limiting circuit 8 is synthesized and distributed with the output voltage of the flyback transformer 5 by the resistors R1 to R3 of the distribution circuit 11 and applied to the cathode ray tube grid terminal G1. It will control the brightness.

That is, the brightness of the monitor can be controlled in a digital manner by increasing or decreasing the negative power applied to the cathode ray tube grid terminal G1 according to the pulse width modulation signal output from the microprocessor 10.

As described above, the present invention, after converting the pulse width modulation signal, which is the brightness control data output from the microprocessor to the voltage through the F / V converter, the cathode ray tube according to the output level of the F / V converter By adding a voltage limiting circuit for changing the voltage of the negative power applied to the grid terminal, and by controlling the screen brightness of the monitor in a digital manner, it is possible to contribute to improving the reliability of the monitor by precisely adjusting the brightness of the screen in multiple stages.

Claims (3)

In the brightness control circuit of the monitor which extracts the negative power by the first negative power output circuit 6 and applies the predetermined voltage generated by the flyback transformer 5 to the cathode ray tube grid terminal G1, the monitor system is A microprocessor 10 for controlling and outputting brightness data as a pulse width modulated signal, an F / V converter 9 for outputting a stable voltage proportional to the pulse width modulated signal output from the microprocessor 10, A voltage limiting circuit 8 for restrictively outputting a voltage proportional to the output level of the F / V converter 9, an output terminal of the voltage limiting circuit 8, and a plurality of resistors R1 to R3 And a distribution circuit (11) which is connected in parallel and in series to synthesize and distribute the output voltages of the voltage limiting circuit (8) and the flyback transformer (5) and apply them to the cathode ray tube grid terminal (G1). The comparator 9a of claim 1, wherein the F / V converter 9 compares a pulse width modulation signal output from the microprocessor 10 with a set reference voltage Vref and outputs a pulse signal as a voltage. A ripple agent connected between an output terminal of the comparator 9a and an inverting terminal (?), And connected in parallel with a resistor R7 and a capacitor C3 to remove a ripple component included in the output voltage of the comparator 9a; The brightness control circuit of the monitor, characterized in that consisting of a reject (9b). The voltage limiting circuit (8) according to claim 1, wherein the voltage limiting circuit (8) is connected to an output side of the F / V converter (9) and outputs a voltage proportionally to the distribution circuit (11) according to an input level, And a resistor (R8 to R10) connected to each end of the transistor (Q) and connected in parallel to the power supply terminal (12V) to limit the output voltage of the transistor (Q).