KR20000028432A - Voltage compensation circuit of horizontal driving transformer in multi mode monitor - Google Patents

Abstract

PURPOSE: A circuit for compensating voltage of a horizontal driving transformer in a multi mode monitor is provided to supply fixed base current to a horizontal output transistor, by flowing the regular current in a first side of the horizontal driving transformer regardless of changes of horizontal frequency according to each mode. CONSTITUTION: A circuit for compensating voltage of a horizontal driving transformer in a multi mode monitor, generating/supplying an induced electromotive force by supplying direct driving voltage, when the horizontal driving transformer turns on/off the horizontal driving transformer(TR1) through a horizontal driving signal, comprises a multi mode monitor, a sawtooth wave signal generator(10), a PWM(Pulse Width Modulation) signal generator(20), a direct voltage generator(30). The saw tooth waveform signal generator generates a sawtoothed waveform signal having same frequency with a square-wave horizontal driving signal. The PWM signal generator generates a PWM signal having a higher a duty rate, as frequency of the sawtoothed waveform is raised. The direct voltage generator supplies higher direct current to the driving voltage of the horizontal driving transformer, by generating size of the direct current which is getting higher, as the duty rate of the PWM signal is raised.

Description

A circuit for compensating a voltage of a horizontal-drive-transformer in a multi-mode monitor

The present invention relates to a voltage compensation circuit of a horizontal drive transformer in a multi-mode monitor. In particular, a constant base current is applied to a horizontal output transistor by flowing a constant current to the primary side of the horizontal drive transformer regardless of a change in the horizontal frequency of each mode. The present invention relates to a voltage compensation circuit of a horizontal drive transformer in a multi-mode monitor intended to be supplied.

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.

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 High resolution mode 64 to 75 60 to 70 1024 * 7681280 * 1024

As shown in Table 1, the horizontal and vertical frequencies are different 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 synchronizing frequency of each mode is about 30 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.

The operation of the horizontal deflection circuit of a general monitor will be briefly described with reference to FIG. 1 as follows.

A horizontal drive signal (H.drive) having a horizontal synchronization frequency (H.sync) output from the video card turns on the horizontal drive transistor (TR1), and the base of the horizontal output transistor (TR2) through the horizontal drive transistor (HDT). Supply current to the terminal.

When the horizontal output transistor TR2 is turned on by receiving sufficient base current, the B ⁺ power supply current of the flyback transformer FBT flows to the horizontal output transistor TR2 through the horizontal deflection coil HD.Y.

As described above, while the transistor TR2 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 HD is rapidly turned off in response to the horizontal drive signal H.driver. The current accumulated in .Y) charges the retrace capacitor RE.C.

When the retrace capacitor RE.C is fully charged, it is discharged back to the horizontal deflection coil HD.Y, and thus current is accumulated in the deflection coil HD.Y. In this way, the period between the charging and discharging of the retrace capacitor RE.C determines the retrace period.

When energy is accumulated in the deflection coil HD.Y so that the deflection coil voltage is such that a forward bias is applied to the damper diode DD, the damper diode DD is conducted and a current flowing through the deflection coil HD.Y. Will fall to zero. At this time, the current flowing through the damper diode D.D corresponds to the first half of the effective scanning period of the horizontal sawtooth wave.

As described above, when the current becomes zero, the horizontal output transistor TR2 is turned on again by the horizontal drive signal H. driver, and the sawtooth current flows through the horizontal deflection coil HD.Y while repeating the above process. A horizontal deflection is made and a horizontal scan is made.

Fig. 2 (a) is a waveform diagram showing a horizontal drive signal at a low frequency, (b) is a waveform diagram showing the primary current of a driving transformer generated by a horizontal synchronization signal at a low frequency, and (a ') is a horizontal diagram at a high frequency. (B ') is a waveform diagram showing the primary side current of the drive transformer generated by the high frequency horizontal synchronization signal.

As described above, when the horizontal drive transistor TR1 is turned on by the horizontal drive signal as shown in FIG. 2 (a) (a '), the primary current of the horizontal drive transformer HDT is shown in FIG. 2 (b) ( b ') increases, and when the horizontal drive transistor TR1 is turned off, the primary side current of the horizontal drive transformer HDT is rapidly decreased and induced to the secondary side, wherein the horizontal drive transformer HDT The current induced to the secondary side of is supplied to the base terminal of the horizontal output transistor (TR2) to drive the horizontal output transistor (TR2).

However, when the horizontal drive signal (H.drive) is cursed, as shown in (b), the primary side current of the horizontal drive transformer (HDT) increases, so that the current induced to the secondary side also increases, and thus the horizontal output. The base current of the transistor TR2 also increases. On the contrary, when the horizontal drive signal (H.drive) has a high frequency, as shown in (b '), the primary side current of the horizontal drive transformer (HDT) decreases, so that the induced current to the secondary side also decreases, and thus the horizontal output. The base current of the transistor TR2 is also reduced. That is, in the conventional horizontal deflection circuit, the base current of the horizontal output transistor TR2 is rapidly changed according to the horizontal frequency, thereby causing a problem that the horizontal output circuit becomes unstable.

Accordingly, the present invention has been made to solve the above problems, by supplying a constant current to the horizontal output transistor by flowing a constant current to the primary side of the horizontal drive transformer irrespective of the change in the horizontal frequency for each mode, multiple An object of the present invention is to provide a voltage compensating circuit of a horizontal drive transformer in a mode monitor.

In the multi-mode monitor according to the present invention for achieving the above object, the voltage compensation circuit of the horizontal drive transformer,

When the horizontal drive transistor is turned on / off by the horizontal drive signal, the horizontal drive transformer receives a DC drive voltage to generate induced electromotive force and supplies the horizontal output transistor to the horizontal output transistor. A sawtooth signal generator for generating the same sawtooth signal; A PWM signal generation unit generating a PWM signal having a higher duty ratio as the frequency of the sawtooth signal increases; And a direct current voltage generating unit generating a direct current voltage having a larger magnitude as the duty ratio of the PWM signal is larger, and supplying it as a drive voltage of the horizontal driving transformer.

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

2 is a signal waveform diagram of each part of FIG. 1;

3 is a circuit diagram showing a voltage compensation circuit of a horizontal drive transformer in a multi-mode monitor according to the present invention;

4 is a signal waveform diagram of each part of FIG. 3.

* Names of symbols according to the main parts of the drawings

10: saw tooth signal generator 20: PWM signal generator

30: DC voltage generating unit Q 11, 12: first and second transistors

C 11,12: Capacitor COM11: Comparator

D11: Diode L11: Inductor

R 11,12: Resistor HDT: Horizontal Drive Transformer

TR1: horizontal drive transistor TR2: horizontal output transistor

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

3 is a circuit diagram showing a voltage compensating circuit of a horizontal drive transformer in a multi-mode monitor according to the present invention.

As shown in FIG. 3, when the horizontal drive transistor TR1 is turned on / off by the horizontal drive signal H.drive, the horizontal drive transformer HDT generates a direct current drive voltage. V _{B +} In the multi-mode monitor to generate the induced electromotive force to supply to the horizontal output transistor (TR2), the sawtooth signal generator (10) for generating a sawtooth signal having the same frequency as the horizontal drive signal (H.drive) of the square wave )Wow ; PWM signal generation unit 20 for generating a PWM signal having a greater duty ratio as the frequency of the sawtooth signal is larger; And as the duty ratio of the PWM signal is larger, a larger DC voltage is generated to generate a driving voltage of the horizontal driving transformer (HDT). V _{B +} It is composed of a DC voltage generator 30 to be supplied to.

Here, the sawtooth signal generator 10 receives a horizontal synchronous signal (H.drive) of a square wave at the base end, the collector end receives the predetermined voltage Vcc1 through the resistor R11, and the emitter end is grounded. 1 transistor Q11; One end is composed of a first capacitor C11 connected in parallel to the collector end of the first transistor Q11 and the other end is grounded, and is determined by turning on / off the first transistor Q11. The voltage) repeatedly charges and discharges the first capacitor C11 to generate a sawtooth wave signal having the same frequency as the horizontal synchronous signal H. drive of the square wave.

In addition, the PWM signal generation unit 20 receives a sawtooth signal in which an inverting (-) input terminal is charged and discharged through the first capacitor C11, and generates a low level signal when the voltage of the sawtooth signal is greater than the reference voltage Vr. It is composed of a comparator (COM) for outputting a high level signal when the output voltage is less than the reference voltage. As the frequency of the sawtooth signal is larger, a PWM signal having a higher duty ratio is generated.

The DC voltage generator 30 further includes: a second transistor Q12 having a gate terminal receiving a PWM signal from the comparator COM and switching a predetermined voltage Vcc2 by the PWM signal; An inductor (L11) for accumulating energy when a current flows through the second transistor (Q12); A diode (D11) which is turned on when the second transistor (Q12) is off to provide a current path for the inductor (L11); And an electrolytic capacitor C12 for removing the ripple, and as the duty ratio of the PWM signal increases, a DC voltage having a larger magnitude is generated to generate a driving voltage of the horizontal driving transformer HDT. V _{B +} ).

Subsequently, the operation and effects of the circuit according to the present invention configured as described above will be described with reference to the waveform diagram of FIG. 4 divided into a case where the horizontal drive signal is a low frequency and a high frequency.

First, in order to maintain a constant current flowing in the primary side of the horizontal drive transformer HDT regardless of the frequency of the horizontal drive signal H. drive, the driving voltage supplied to the horizontal drive transformer HDT V _{B +} ) Should be changed in proportion to the frequency of the H.drive.

The rate of increase of the primary current of the horizontal drive transformer (HDT) ) Is determined as in Equation 1 below.

When the horizontal drive signal H.drive is cursed, as shown in FIG. 2 (b), the primary current increase rate of the horizontal drive transformer HDT ( When the horizontal drive signal (H.drive) is a high frequency, as shown in FIG. 2 (b '), the increase rate of the primary current of the horizontal drive transformer (HDT) ) Decreases, and when the horizontal drive signal (H.drive) is a high frequency, the increase rate of the primary current of the horizontal drive transformer (HDT) ( Driving voltage supplied to the horizontal drive transformer (HDT) to increase V _{B +} ) Should be increased.

4 (a) is a waveform diagram showing a low frequency horizontal drive signal, (b) is a waveform diagram showing a sawtooth signal generated by the low frequency horizontal synchronization signal, (c) is a waveform diagram showing a low frequency sawtooth signal (A ') is a waveform diagram showing a high frequency horizontal drive signal, and (b') is a waveform diagram showing a sawtooth signal generated by a high frequency horizontal synchronization signal. (C ') is a waveform diagram showing a PWM signal generated by a sawtooth wave signal of a high frequency frequency.

First, the horizontal drive signal (H.drive) having the horizontal synchronization frequency (H.sync) output from the video card turns on the horizontal drive transistor (TR1), and through the horizontal drive transistor (HDT) of the horizontal output transistor (TR2) Supply current to the base terminal.

1. When the horizontal drive signal is low frequency

At this time, when the horizontal synchronous signal H.drive of the square wave as shown in FIG. 4 (a) (a ') is input to the base terminal of the first transistor Q11, the horizontal drive signal H.drive is applied. The voltage Vcc1 is charged to the first capacitor C11 through the resistor R11 at the high level, and the voltage charged to the first capacitor C11 when the horizontal drive signal H.drive is at the low level. Is discharged.

The first capacitor C11 repeats charging and discharging by the horizontal drive signal H. drive to generate a sawtooth wave signal as shown in FIG. 4 (b) (b '). In this case, the sawtooth signal has the same frequency as the horizontal synchronous signal (H.drive) of the square wave.

The sawtooth signal is input to the inverting (-) input terminal of the comparator COM11. Accordingly, the comparator COM11 compares the voltage of the sawtooth signal with a reference voltage Vr, so that the voltage of the sawtooth signal is a reference voltage Vr. If it is larger than this, a low level signal is output and if it is smaller than the reference voltage Vr, a high level signal is output, thereby generating a PWM signal as shown in Fig. 4C (C ').

In this case, as shown in FIG. 4, as the frequency of the sawtooth signal increases, the duty ratio of the PWM signal increases.

The PWM signal is input to the gate terminal of the second transistor Q12, and accordingly, the second transistor Q12 switches the predetermined voltage Vcc2 by the PWM signal to inductor L11 and the second capacitor C12. Output DC voltage through).

Looking at the operation of the DC voltage generator 30 in detail, when the PWM signal is at a high level, the second transistor Q12 is turned on so that the voltage between the drain and source of the second transistor Q12 drops to 0V. The current flowing through the second transistor Q12 is increased.

At this time, a voltage is applied to the diode D11 in the reverse direction to turn the diode D11 off, and a difference between the input voltage and the output voltage is applied to the inductor L12 so that a current flowing through the inductor L11 is applied to the second transistor Q12. Gradually increase over time.

On the other hand, when the PWM signal goes low and the second transistor Q12 is turned off, a voltage appears between the drain and the source of the second transistor Q12, and a counter electromotive force is generated in the inductor L11 so that the diode D11 is turned on. The current flowing through the second transistor Q1 flows through the diode D11.

At this time, since the voltage induced in the inductor L11 is in the opposite direction as when the second transistor Q12 is turned on, the current flowing through the inductor L11 gradually decreases. The current flowing through the second transistor Q12 becomes '0'.

As described above, the magnitude of the DC voltage output from the DC voltage generator 30 is equal to the magnitude of the input DC voltage Vcc2 and the turn-on time of the second transistor Q12 as shown in Equation 2 below. T _on ) And turnoff time ( T _off Determined by).

As represented by Equation 2, the turn-on time of the second transistor Q12 T _on Is longer, the output voltage Vo of the DC voltage generator 30 becomes higher. At this time, as the duty ratio of the PWM signal is larger, that is, the longer the high level period, the turn-on time of the second transistor Q12 is increased. T _on ) Lengthens.

That is, the DC voltage generator 30 generates a DC voltage having a larger magnitude as the duty ratio of the PWM signal is larger, thereby driving the driving voltage of the horizontal driving transformer HDT. V _{B +} ).

As described above, according to the present invention, the lower the frequency of the horizontal drive signal (H.drive), the lower the driving voltage supplied to the horizontal drive transformer (HDT). V _{B +} ) And conversely, the higher the frequency of the horizontal drive signal H.drive, the higher the driving voltage supplied to the horizontal drive transformer HDT. V _{B +} ) To maintain a constant current induced in the secondary side of the horizontal drive transformer (HDT), thereby maintaining a constant base current supplied to the horizontal output transistor (TR2) regardless of the change in the horizontal frequency for each mode. This has the effect of improving the reliability of the horizontal output transistor TR2 and the life of the whole set.

Claims (4)

When the horizontal drive transistor TR1 is turned on / off by the horizontal drive signal H.drive, the horizontal drive transformer HDT causes the DC drive voltage ( V _{B +} In the multi-mode monitor that generates the induced electromotive force is supplied to the horizontal output transistor (TR2), A sawtooth signal generator 10 for generating a sawtooth signal having the same frequency as the horizontal drive signal H. drive of the square wave; PWM signal generation unit 20 for generating a PWM signal having a greater duty ratio as the frequency of the sawtooth signal is larger; And As the duty ratio of the PWM signal is larger, a larger DC voltage is generated to generate a driving voltage of the horizontal driving transformer HDT. V _{B +} Voltage compensation circuit of a horizontal drive transformer in a multi-mode monitor, characterized in that consisting of a DC voltage generator (30) for supplying. The sawtooth signal generator 10 according to claim 1, A first transistor Q11 receiving a horizontal synchronous signal H.drive of a square wave at a base end, a collector end receiving a predetermined voltage Vcc1 through a resistor R11, and an emitter end being grounded; One end is composed of a first capacitor C11 connected in parallel to the collector end of the first transistor Q11 and the other end is grounded, When the first transistor Q11 is turned on / off, a predetermined voltage () is repeatedly charged and discharged to the first capacitor C11 to generate a sawtooth wave signal having the same frequency as the horizontal synchronous signal (H.drive) of the square wave. And a voltage compensation circuit of a horizontal drive transformer in a multi-mode monitor. The method of claim 2 wherein the PWM signal generation unit 20, The inverting (-) input terminal receives the sawtooth signal charged and discharged through the first capacitor C11 and outputs a low level signal if the voltage of the sawtooth signal is greater than the reference voltage Vr, and outputs a high level signal if the voltage is less than the reference voltage. It consists of comparator (COM) to output, And a PWM signal having a higher duty ratio as the frequency of the sawtooth signal increases, wherein the voltage compensation circuit of the horizontal driving transformer is used. The DC voltage generator 30 of claim 3, A second transistor Q12 having a gate terminal receiving a PWM signal from the comparator COM and switching a predetermined voltage Vcc2 by the PWM signal; An inductor (L11) for accumulating energy when a current flows through the second transistor (Q12); A diode (D11) which is turned on when the second transistor (Q12) is off to provide a current path for the inductor (L11); And Consists of electrolytic capacitor (C12) for removing ripple, As the duty ratio of the PWM signal is larger, a larger DC voltage is generated to generate a driving voltage of the horizontal driving transformer HDT. V _{B +} Voltage compensation circuit of a horizontal drive transformer in a multi-mode monitor.