KR19990003616U - Horizontal Driving Pulse Width Control Circuit of Multi-Mode Monitor - Google Patents

Abstract

The present invention relates to a circuit for supplying a constant base current to a horizontal output transistor by controlling the horizontal drive pulse width in a multi-mode monitor.

In the circuit of the present invention, the horizontal drive signal (H.drive) is turned on and off the horizontal drive transistor (Q1) and amplified through the horizontal drive transformer (HDT) is applied to the base end of the horizontal output transistor (Q2) In a horizontal deflection circuit of a monitor in which the horizontal output transistor Q2 is turned on / off and a sawtooth current flows through the horizontal deflection coil H.DY, a predetermined DC voltage is applied from the microcomputer to provide a predetermined pulse width. A horizontal oscillation IC 10 for outputting a horizontal drive signal H.drive, and a driving current sensing unit for detecting a base current I _B1 of the horizontal output transistor Q2 and outputting a pulse width control voltage B; 20), the base current of the horizontal output transistor is sensed to control the horizontal drive pulse width, and accordingly supply a constant base current to protect the transistor to perform a stable horizontal deflection operation. All.

Description

A pulse-width control circuit of horizontal drive in a multi-mode monitor

The present invention relates to a horizontal output transistor that performs an on / off switching operation to supply a sawtooth current to a horizontal deflection coil of a multimode monitor. In particular, the horizontal driving pulse width can be adjusted to control the base current of the horizontal output transistor. The present invention relates to a horizontal drive pulse width control circuit of a multi-mode monitor.

In general, a multi-mode monitor reproduces a video image in accordance with a signal received from a video card in a computer, which requires adjustment of each part of the circuit according to a timing parameter of the received signal.

Here, look at the classification of the monitor according to the video mode through Table 1.

TABLE 1

Classification by video mode

Video mode Horizontal frequency (KHz) Vertical frequency (Hz) Resolution (H * V) CGA 15.75 60 640 * 200 EGA 21.8 60 640 * 350 VGA 31.5 60/70 720 * 350 640 * 480 SVGA 35 to 37 INTERLACE 1024 * 768 800 * 600 High resolution mode 48-75 60-70 1024 * 7681280 * 1024

As shown in Table 1, horizontal and vertical frequencies differ according to the modes supported by the video card, and in particular, a video card supporting various modes, for example, a video card supporting VGA and SVGA and high resolution only modes, is mounted on the monitor. If so, the range of the horizontal frequency of each mode is about 31 KHz to 75 KHz.

That is, when the mode is changed in the multi-mode monitor, there are parts that need to be changed in the internal circuits of the monitor. For example, the size and position of the image, the horizontal and vertical synchronization, the optimization of the deflection unit, and the various deflection correction circuits Readjustment should be done.

Referring to the horizontal deflection circuit of FIG. 1, the deflection circuit operation of a general monitor will be briefly described as follows.

The horizontal synchronization signal H.sync output from the video card (not shown) is appropriately signal-modulated from the horizontal oscillation IC 10 to the horizontal driving signal H.drive and supplied to the horizontal driving transistor Q1.

The horizontal driving signal H.drive turns on the horizontal driving transistor Q1 and supplies current to the base terminal of the horizontal output transistor Q2 through the horizontal driving transformer HDT.

When the horizontal output transistor Q2 is turned on with sufficient base current, the B ⁺ power supply current of the flyback transformer FBT (not shown) flows to the horizontal output transistor Q2 through the horizontal deflection coil H.DY. .

Thus, while the horizontal output transistor Q2 is turned on, it corresponds to the second half of the effective scanning period of the horizontal sawtooth wave, and then the horizontal deflection coil Q2 is rapidly turned off according to the horizontal drive signal H.drive. The current accumulated in (H.DY) charges the retrace capacitor (Cr). When the retrace capacitor Cr is fully charged, it is discharged back to the horizontal deflection coil H. DY, and thus, all energy is accumulated in the horizontal deflection coil H. DY.

In this way, the period between the charging and discharging of the retrace capacitor Cr determines the retrace period.

Subsequently, when all the energy is accumulated in the horizontal deflection coil H.DY, and the voltage of the horizontal deflection coil H.DY is such that the forward bias is applied to the damper diode Dd, the damper diode Dd becomes conductive. The current flowing through the horizontal deflection coil (H.DY) gradually returns to zero. At this time, the current flowing through the damper diode Dd corresponds to the first half of the effective scanning period of the sawtooth wave.

As described above, when the current reaches zero, the horizontal output transistor Q1 is turned on again by the H. drive signal, and the horizontal sawtooth current flows through the horizontal deflection coil H.DY while repeating the above process. Deflection is made.

On the other hand, since the pulse width of the horizontal drive pulse is determined by receiving a DC voltage (for example, + 12V) applied from a microcomputer not shown by the pulse width adjustment terminal H. Duty of the horizontal drive pulse, the pulse width is fixed. At this time, the base current I _B1 of the horizontal output transistor Q2 decreases when the pulse width of the horizontal drive pulse is large, whereas the base current IB1 increases when the pulse width of the horizontal drive pulse is small.

However, when the base current of the horizontal output transistor is increased, the horizontal output transistor is destroyed, so that the pulse width of the horizontal driving pulse should be increased to reduce the base current, and if the base current is small, the pulse width of the horizontal driving pulse should be decreased. As described above, since the pulse width is fixed, the horizontal output transistor is destroyed.

In order to solve the above problems, the present invention is designed to detect the base current of the horizontal output transistor and adjust the horizontal driving pulse width to control the horizontal driving pulse width control circuit of the multi-mode monitor. The purpose is to provide.

In the circuit of the present invention for achieving the above object, the horizontal drive signal is turned on / off the horizontal drive transistor and amplified by the horizontal drive transformer is applied to the base end of the horizontal output transistor to turn on / off the horizontal output transistor In the horizontal deflection circuit of a monitor in which a sawtooth current flows through the horizontal deflection coil, a horizontal oscillation IC for applying a predetermined DC voltage from a microcomputer to output a horizontal drive signal having a predetermined pulse width, and a horizontal output transistor. Characterized in that the drive current sensing unit for outputting a pulse width control voltage by sensing the base current.

1 is a circuit diagram showing a horizontal deflection circuit of a general multi-mode monitor;

2 is a circuit diagram illustrating a horizontal driving pulse width control circuit of a multi-mode monitor according to the present invention;

3 is a waveform diagram showing the relationship between the horizontal drive pulse width and the base current according to the present invention.

＊ Explanation of symbols for main parts of drawing

10: horizontal oscillation IC 20: drive current detection unit

Q1: horizontal drive transistor Q2: horizontal output transistor

HDT: Horizontal Drive Transformer Q3: NPN Transistor

Dd: Damper Diode Cr: Return Capacitor

H.DY: Horizontal deflection coil Q3: NPN type transistor

R1, R2, R3, R4, R5: Resistance

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram illustrating a horizontal driving pulse width control circuit of a multi-mode monitor according to the present invention.

As shown in FIG. 2, the circuit of the present invention includes a horizontal oscillation IC 10, a driving current sensing unit 20, a horizontal driving transistor Q1, a horizontal output transistor Q2, a horizontal driving transformer HDT, and the like. Consists of.

In addition, the driving current detection unit 20 is connected to the primary winding of the horizontal drive transformer (HDT) through the collector terminal through the resistor (R1) and the base end of the horizontal drive transformer (HDT) through the resistor (R2). NPN type transistor Q3 connected to the secondary winding and having an emitter terminal grounded through resistor R3, a current sensing resistor R4 connected to the emitter terminal of transistor Q3, and between resistor R4 and ground. It consists of a resistor (R5) connected to.

First, the case where the base current I _B1 of the horizontal output transistor Q2 is high will be described.

When a large amount of current flows through the base terminal of the horizontal output transistor Q2, the voltage of the node A is increased. As a result, a high voltage is applied to the base terminal of the NPN transistor Q3, and the NPN transistor Q3 is turned on. Therefore, the collector current of the NPN transistor Q3 flows to the emitter stage, and the emitter current increases because the emitter current is proportional to the base current.

Accordingly, the current Isens flowing through the resistor R5 increases to increase the voltage of the node B, that is, the pulse width control voltage, and as the pulse width control voltage increases, the horizontal driving pulse width increases to increase the horizontal output transistor Q2. The base current I _B1 is lowered.

Next, a case where the base current I _B1 of the horizontal output transistor Q2 is small will be described. Since the base current I _B1 is small, the voltage of the node A is lowered and is output from the emitter terminal of the NPN transistor Q3 so that the resistance ( The current Isens flowing to R5) decreases, thereby reducing the voltage of the node B, that is, the pulse width control voltage.

As a result, the horizontal driving pulse width is decreased to increase the base current I _B1 of the horizontal output transistor Q2.

That is, the base current (I _B1) is When the pulse width of the control voltage (B) a lower horizontal drive pulse width smaller when smaller to increase the amount the base current (I _B1), the base current (I _B1) as shown in Figure 3 When is large, the base current I _B1 is lowered when the pulse width control voltage B is increased to increase the horizontal driving pulse width.

As described above, the circuit of the present invention senses the base current of the horizontal output transistor and adjusts the horizontal driving pulse width so that a constant current is always applied to the horizontal output transistor, thereby causing thermal runaway of the horizontal output transistor. It is effective to prevent the movement and make stable horizontal deflection operation.

Claims (2)

The horizontal drive signal H.drive turns the horizontal drive transistor Q1 on and off, is amplified by the horizontal drive transformer HDT, and is applied to the base terminal of the horizontal output transistor Q2 so as to supply the horizontal output transistor Q2. In a horizontal deflection circuit of a monitor which is turned on / off and thus a sawtooth current flows through a horizontal deflection coil (H.DY), A horizontal oscillation IC 10 for outputting a horizontal drive signal H. drive having a predetermined pulse width by applying a predetermined DC voltage from the microcomputer; And Horizontal drive pulse width control circuit of the multi-mode monitor characterized in that the drive current sensing unit 20 for detecting the base current (I _B1 ) of the horizontal output transistor (Q2) and outputs the pulse width control voltage (B). . The driving current sensing unit 20 of claim 1, wherein the collector current is connected to the primary winding of the horizontal drive transformer HDT through a resistor R1 and the base end is a horizontal drive transformer through a resistor R2. An NPN transistor Q3 connected to the secondary winding of the HDT and having an emitter terminal grounded through a resistor R3; A current sense resistor R4 connected to the emitter terminal of the transistor Q3; And a resistor (R5) connected between the resistor (R4) and ground.