CN100583196C - A method and system for realizing soft startup of display device - Google Patents

Abstract

The invention provides a method for realizing equipment soft start and a system. Said method includes steps as follows: a. line frequency energizing impulse inputted into line output pipe by wipe circuit is cut off firstly when display equipment start, converter circuit inputs line frequency energizing impulse into wipe circuit, its frequency is higher or equal to lowest line scanning frequency of display equipment in normal working, said wipe circuit outputs said line frequency energizing impulse into line output pipe of said display equipment; b. said converter circuit outputs line frequency energizing impulse of normal line scanning frequency into said wipe circuit when control electrical source of automatic frequency control AFC circuit and frequency dividing circuit of said display equipment scanning part reaching stabile working state.

Description

A kind of method and system that realize the CRT soft startup of display device

Technical field

The present invention relates to the video display technology field, particularly the soft start of CRT display device.

Background technology

CRT (cathode-ray tube (CRT)) display device mainly comprises CRT TV and CRT monitor, and it is a kind of electron beam scanning device of realizing electrical-optical conversion, reproduced image.

Fig. 1 is the schematic circuit diagram of CRT display device line scanning part, and wherein Q is a line output valve, and D is a damper diode, and C is a retrace interval capacitor, and Lt is the linearity correction inductance, and Lh is the inductance of the deflection coil of line direction, and Cs is the S corrective capacity, and FBT is a horizontal equilibrium flyback transformer.

Fig. 2 is the equivalent circuit schematic of Fig. 1, and wherein, line output valve and damper diode are reduced to switch, because Lt＜＜Lh, so Lt can be reduced to short circuit, promptly ignore its influence.Because the value of Cs is bigger, can be reduced to ac short circuit again, and the average voltage at Cs two ends equaling supply voltage, is constant in the course of the work substantially, can equivalence be a direct voltage source Vcc.The inductance L p of the elementary winding of the kickback transformer FBT LH that becomes among Fig. 2 in parallel with the inductance L h of line deflector coil.

Fig. 3 is scan current waveform figure, and wherein each physical quantity is described as follows:

TH is the line traversal time, and Tr is the line scanning retrace interval, and sum of the two is a complete scan period T (t1 among the figure～t6).Deflection current over time, is divided into several time period t 0～t6 to the whole cycle again in one-period for convenience of explanation.

Iy is the electric current that flows through line deflector coil, sweep current at once, and trace is sawtooth wave, flyback is a Sasser.Preceding half section of the trace sawtooth wave flows through damper diode, and the second half section is flow through line output valve.

Vb is a row energization voltage, is square wave, acts on the line output valve base stage.

Vfb is flyback voltage (being flyback voltage), is pulsating wave, acts between the line output valve C utmost point and the E utmost point.

The following expression formula of deriving horizontal deflection electric current I y and line retrace voltage Vfb respectively therefrom find out the two and the relation of line frequency, and then which type of influence demonstration line frequency variation meeting causes to them.

Horizontal deflection electric current I y is in the scan(ing) stroke second half section (t0～t1 is in t5～t6 time), and the switch S q among Fig. 2 (line output valve) conducting determines deflection current Iy jointly by inductance L h and power Vcc at this moment, and electric current I y is linear to rise.

$\mathrm{Iy}=\frac{1}{\mathrm{Lh}}{\∫}_0^t\mathrm{Vcc}*\mathrm{dt}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}(t-t0)$

When t=t1,

$\mathrm{Iyp}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}(t1-t0)=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{\mathrm{Ts}}{2}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{T-\mathrm{Tr}}{2}$ (formula 1)

Reach maximal value, electron beam is also corresponding to be scanned up to the screen rightmost from screen center.

Ts is the scan(ing) stroke time in the following formula.Preceding half section of scan(ing) stroke (t3～t5), the switch S d among Fig. 2 (damper diode) conducting, same reason, electric current I y rises to zero by-Iyp linearity, and electron beam is scanned up to screen center from the screen Far Left.

Tr during the scan retrace, switch S Q, SD all disconnect, and inductance L h and retrace interval capacitor C produce free oscillation.The length of retrace interval depends on the free period, and equals the free period half.Represent retrace interval with Tr, then

$\mathrm{Tr}=\mathrm{\π}\sqrt{\mathrm{Lh}*C}$

In the following formula, T is the line-scanning period, T=Ts+Tr.

2, line retrace voltage

The voltage U c=U+Vcc at retrace interval C two ends, and ULh is produced by resonance, thereby have

ULh＝ω*Lh*Iy

Its maximal value is

Uyp＝ω*Lh*Iyp

Following formula $\mathrm{\ω}=\frac{1}{\sqrt{\mathrm{Lh}*C}}=\frac{\mathrm{\π}}{\mathrm{Tr}}$

Thereby can get

$\mathrm{Uyp}=\frac{\mathrm{\π}}{\mathrm{Tr}}*\mathrm{Lh}*\mathrm{Iyp}=\mathrm{Vcc}*\frac{\mathrm{\π}}{2}*\frac{\mathrm{Ts}}{\mathrm{Tr}}$

Line output valve collector and emitter both end voltage Uce equal capacitor C both end voltage Uc, promptly

$\mathrm{Uc}=\mathrm{Uce}=\mathrm{Uyp}+\mathrm{Vcc}=\mathrm{Vcc}*(1+\frac{\mathrm{\π}}{2}*\frac{\mathrm{Ts}}{\mathrm{Tr}})$

$=\mathrm{Vcc}*(1+\frac{\mathrm{\π}}{2}*\frac{T-\mathrm{Tr}}{\mathrm{Tr}})$

$=\mathrm{Vcc}*[1+\frac{\mathrm{\π}}{2}*(\frac{T}{\mathrm{Tr}}-1)]$ (formula 2)

From formula 1 and formula 2 as can be known, line-scanning period T is long more, then flows through line output valve current peak Iyp and put on the voltage peak Vcp at collector and emitter two ends big more.The CRT display device starts moment, because the power supply of AFC (automatic frequency control) circuit and frequency dividing circuit does not also reach the minimum voltage value of steady operation, cause the row energization pulsed frequency possible unstable, if this underfrequency, safety to line output valve is very unfavorable, originally have one, two cycle line output valve ON time long, the electric current and the flyback voltage peak value that flow through line output valve may surpass limit value, and line output valve just may be damaged.

Summary of the invention

The object of the present invention is to provide a kind of method and system of the CRT of realization soft startup of display device, the low excessively problem that causes line output valve to damage of row energization pulsed frequency when being intended to solve the CRT display device startup that exists in the prior art.

For achieving the above object, the present invention adopts following technical scheme:

A kind of method that realizes the CRT soft startup of display device, described method comprises the steps:

When a, the startup of CRT display device, turn-off the line frequency driving pulse that sweep circuit is defeated by line output valve earlier, frequency changer circuit is to sweep circuit output line frequency driving pulse, minimum line-scanning frequency when its frequency is greater than or equal to CRT display device operate as normal, described sweep circuit is exported described line frequency driving pulse to the line output valve of described CRT display device;

B, when the power supply of the automatic frequency of described CRT display device sweep test control AFC circuit and frequency dividing circuit reaches steady-working state, described frequency changer circuit is to the line frequency driving pulse of described sweep circuit output normal row sweep frequency.

Wherein step a specifically comprises:

When a1, the startup of CRT display device, give the register assignment of control line-scanning frequency in the described frequency changer circuit, described frequency changer circuit is exported described line frequency driving pulse to described sweep circuit, the minimum line-scanning frequency when its frequency is greater than or equal to CRT display device operate as normal;

A2, described sweep circuit are exported described line frequency driving pulse to the line output valve of described CRT display device;

Wherein step b specifically comprises:

The power supply testing circuit of b1, described sweep circuit detects the AFC circuit of automatic frequency gated sweep part of described CRT display device and whether the power supply of frequency dividing circuit reaches steady-working state, if change step b2, otherwise change step a;

B2, described frequency changer circuit progressively are reduced to the normal row sweep frequency with the line frequency driving pulse frequency of its output.

Wherein step b specifically comprises:

B1, described frequency changer circuit judge whether it reaches the default time to the time that sweep circuit output line frequency driving pulse continues, if change step b2, otherwise change step a;

B2, described frequency changer circuit progressively are reduced to the normal row sweep frequency with the line frequency driving pulse frequency of its output.

Wherein step b2 specifically comprises:

Described frequency changer circuit progressively is reduced to the normal row sweep frequency according to step number and the step-length that predefined line frequency changes with described line frequency driving pulse frequency.

The present invention also provides a kind of system of the CRT of realization soft startup of display device, comprises line output valve,, described system comprises:

Frequency changer circuit, be used in the process that the CRT display device starts the line frequency driving pulse of minimum line-scanning frequency when the sweep circuit output frequency is greater than or equal to CRT display device operate as normal, and be used for after the power supply of the AFC circuit of described CRT display device sweep test and frequency dividing circuit reaches line frequency driving pulse from steady-working state to described sweep circuit output normal row sweep frequency;

Sweep circuit links to each other with described frequency changer circuit, is used for the line frequency driving pulse of described frequency changer circuit input is outputed to line output valve.

Described frequency changer circuit also comprises the register of controlling line-scanning frequency, and the value that described frequency changer circuit is composed described register according to system is determined the frequency of the line frequency driving pulse that it is exported.

Described CRT display device is a CRT monitor.

The present invention overcomes the deficiencies in the prior art, adopts the row energization signal by frequency conversion IC output upper frequency when the CRT display device starts line scanning, and the low high pressure that produces of frequency impacts to line output valve when avoiding because of device start; After treating CRT display device operate as normal, again in the regular hour, the row energization pulsed frequency is dropped to the technical scheme of standard line frequency step by step, technical solution of the present invention is utilized existing frequency conversion IC in the CRT display device, so need not increase any hardware cost, realize protection to line output valve; And, the frequency of row energization can be according to the actual conditions setting when CRT display device started, the frequency of soft start is to the transit time between the normal working frequency---and the frequency conversion time also can be provided with flexibly, this is provided with the conversion that can make sweep frequency and becomes very soft level and smooth, as long as this change, and the step number and the step-length of time splitting can realize easily.

Description of drawings

Fig. 1 is the schematic circuit diagram of existing C RT display device line scanning part;

Fig. 2 is the equivalent circuit schematic of Fig. 1;

Fig. 3 is scan current waveform figure in the prior art;

Fig. 4 is the theory diagram of the embodiment of the invention;

Fig. 5 is the program flow diagram of the embodiment of the invention one.

Fig. 6 is the process flow diagram of the embodiment of the invention two.

Embodiment

Ultimate principle of the present invention is to utilize the row energization pulse signal of the output upper frequency when display device starts line scanning of existing frequency conversion IC in the display device, and the row energization pulsed frequency is crossed the low high pressure that produces line output valve is impacted when avoiding because of device start; After the equipment operate as normal to be shown, in the regular hour, the row energization pulsed frequency is dropped to the standard line frequency step by step again, thereby reach the purpose that the guard rows efferent duct is not damaged when starting.

In order to make purpose of the present invention, technical scheme and advantage clearer,, the present invention is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.

As stated in the Background Art, line output valve current peak Iyp and to put on the important parameter of these two line-scan circuits of voltage Vc between line output valve C-E two electrodes relevant with the line-scanning period improves line frequency (reducing line-scanning period T) and can reduce Iyp and reduce Vc.

In addition, generally adopt frequency conversion IC in the CRT display device at present, the frequency of the line synchronizing signal of its output can be controlled by programming, therefore, can be by the row energization signal of frequency conversion IC output output upper frequency when display device starts line scanning, after the equipment operate as normal to be shown, in the regular hour, the row energization pulsed frequency is dropped to the standard line frequency step by step again, the line output valve current peak Iyp when reaching the CRT display device and starting and put on the purpose of the voltage Vc value between line output valve C-E two electrodes.

The theory diagram of the embodiment of the invention as shown in Figure 4, wherein, frequency changer circuit part can produce the line frequency excitation pulse signal of changeable frequency and give sweep circuit; Sweep circuit partly produces the row energization signal and gives line output valve, and can open or turn-off the row energization signal.

Frequency conversion IC adopts PW1225 in the embodiment of the invention, there is the register of a control line-scanning frequency its inside, the height of its value decision line-scanning frequency, the on duty of this register is exactly required line frequency with factor K, and the value that changes this register just can change line-scanning frequency.Factor K among the PW1225=20.94 are determined by chip manufacturer;

Scans I C adopts TDA9116, and it has the functional circuit of the line-scanning frequency of the signal source of following, and row energization pulsed drive line output valve is provided, the register that it also has its power supply of sign whether to stablize, the value of this register is 1, the expression power supply is up to standard, be 0, then deny.

Start moment at televisor, the power supply of the AFC of sweep circuit (automatic frequency control) circuit and frequency dividing circuit does not also reach the minimum voltage value of steady operation, the possible instability of frequency that causes the row energization pulse of TDA9116 output, if this underfrequency, safety to line output valve is very unfavorable, originally have one, two cycle line output valve ON time long, the electric current and the flyback voltage peak value that flow through line output valve may surpass limit value, just may cause line output valve to damage.For the guard rows efferent duct is not damaged when televisor starts; the present invention adopts the soft start scheme: when starting line frequency is risen to 48kHz; make it to be higher than normal scan frequency 31.5kHz; after treating that start-up course finishes, allow line-scanning frequency become the line-scanning frequency 31.5kHz of operate as normal reposefully by the 48kHz substep with the regular hour again.

As mentioned above, the line frequency of 48KHz only has needs when starting, after start-up course finishes, the power supply of AFC (automatic frequency control) circuit and frequency dividing circuit is operated in after the steady state (SS), line frequency need return to normal 31.5kHz (the normal line-scanning frequency of televisor), the process that needs to carry out transition after start-up course finishes, i.e. reduction line frequency progressively, therefore, how to judge that start-up course finishes to become the problem that needs solution, adopt two kinds of schemes to solve in the embodiment of the invention: the one, rule of thumb be worth, preestablish certain start-up time, the pulse signal of frequency conversion IC output 48KHz in the default time after the default time expires, begins to carry out transient process; The 2nd, carry out the detection of power supply by scans I C, when scans I C detects power supply when up to standard, then with the line frequency of 48KHz progressively reduce to 31.5kHz, below be divided into two embodiment and describe:

Embodiment one:

The embodiment of the invention one flow process specifically comprises following step as shown in Figure 5:

1, starts moment at televisor, disconnect the line frequency excitation pulse signal that TDA9116 exports to line output valve by a register by the CPU executive routine;

2, give the register assignment xo=2304 of decision line frequency size among the frequency conversion IC PW1225, and be calculated as follows line frequency:

fo＝K×xo

＝20.94×2304

＝48kHz

3, the CPU executive routine is connected the row energization pulse output of TDA9116, and 48kHz line frequency driving pulse is offered line output valve, to reduce electric current and the voltage that line output valve was born.

4, the signal of frequency conversion ICPW1225 output 48kHz continues the regular hour;

48kHz line frequency driving pulse is offered line output valve, the line frequency driving pulse of this frequency must continue the regular hour, make the CRT monitor part reach stable duty, the length of institute's duration is suitable from starting to the stable time with supply voltage, and this time period can be passed through program setting;

5, whether the default duration of system's judgement expires, if change step 6, otherwise change step 4;

6, carry out transient process, reduce line frequency step by step to normal value;

7, after the row energization pulsed frequency of frequency conversion IC output is reduced to normal value, recover to be input to the line synchronizing signal of frequency conversion IC.

The transition of line frequency, total requirement are to want held stationary, avoid sudden change, and line output valve is impacted, and for this reason, are provided with controlled variable in the program---step number m and step-length n that line frequency changes:

If m=16 promptly divided for 16 steps finished transition,

Because the sweep frequency during operate as normal is 31.5kHz, corresponding xn=1504 then can be got by formula 3,

n＝(xo-xn)/m

＝(2304-1504)/16

＝50

Promptly in the soft start-up process of televisor, its line-scanning frequency with each minimizing 1047Hz (=50*20.94), divided for 16 steps carried out the transition to normal value reposefully from the startup value.

Above-mentioned example explanation will change line frequency, as long as change the value x of the register of decision line frequency in program, it is very easy implementing.

Embodiment two

The flow process of present embodiment as shown in Figure 6, the scans I C of employing (as TDA8380) has self power supply measuring ability, this scans I C provides the result with testing result with a flag register, its state is that 1 expression power supply is up to standard.Whether therefore program can read the state of this register, full with this precondition of judging transition, when it is 1, carries out transition.

Except different among step 5 and the embodiment one, basic identical among other step and the embodiment one, this does not give unnecessary details in the present embodiment, to being described as follows of step 5:

5, whether scans I C detection power supply reaches normal value, if change step 6, otherwise change step 4.

For the ease of further understanding effect of the present invention, provide a quantity notion below by concrete calculating, to look to adopt under soft start measure whether two kinds of situations, line output valve output current and the voltage that is born have actually--great difference.

Because of T=1/f, substitution formula 1 and formula 2 can get:

$\mathrm{Iyp}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{T-\mathrm{Tr}}{2}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{1/f-\mathrm{Tr}}{2}$

$\mathrm{Uc}=\mathrm{Vcc}*[1+\frac{\mathrm{\π}}{2}*(\frac{T}{\mathrm{Tr}}-1)]=\mathrm{Vcc}*[1+\frac{\mathrm{\π}}{2}*(\frac{1}{\mathrm{fTr}}-1)]$

F in the following formula is respectively with fo=48k, the fn=31.5k substitution, and Tr is with the 5.6us substitution, for ease of just comparing,

The voltage peak Vcp at line output valve current peak Iyp when representing just to start and collector and emitter two ends with Iypo and Uco, the voltage peak Vcp at line output valve current peak Iyp when representing operate as normal and collector and emitter two ends with Iypn and Ucn.

Then have respectively

$\mathrm{Iypo}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{1/48000-5.6/{10}^6}{2}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{0.73}{96000}$

$\mathrm{Iypn}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{1/31500-5.6/{10}^6}{2}=\frac{\mathrm{Vcc}}{\mathrm{Lh}}*\frac{0.82}{63000}$

Last two formulas are divided by,

Iypo/Iypn＝0.58

As seen when starting just, adopt after the soft start measure, the current peak of line output valve reduced during than operate as normal near half, as long as so the parameter of line output valve can satisfy the needs of operate as normal, it burns possibility when starting very little.

The result of calculation of flyback voltage is as follows:

$\mathrm{Uco}=\mathrm{Vcc}*[1+\frac{\mathrm{\π}}{2}*(\frac{1}{48000*5.6*{10}^{-6}}-1)]=\mathrm{Vcc}*5.27$

$\mathrm{Ucn}=\mathrm{Vcc}*[1+\frac{\mathrm{\π}}{2}*(\frac{1}{31500*5.6*{10}^{-6}}-1)]=\mathrm{Vcc}*8.3$

Last two formulas are divided by,

Uco/Ucn＝0.63

This shows, also much lower during voltage ratio operate as normal that line output valve collection-emitter-base bandgap grading is born when starting just, thereby line output valve does not just have breakdown danger yet.

As mentioned above, adopt technical scheme of the present invention to realize protection, utilize the existing frequency conversion IC of display device to realize the soft start of line output valve, need not increase any cost on the hardware line output valve; And, the frequency of row energization can be according to the actual conditions setting when CRT display device started, the frequency of soft start is to the transit time between the normal working frequency---and the frequency conversion time also can be provided with flexibly, this is provided with the conversion that can make sweep frequency and becomes very soft level and smooth, as long as this change, and the step number and the step-length of time splitting can realize easily.

The above only is preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of being done within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1, a kind of method that realizes the CRT soft startup of display device is characterized in that, described method comprises the steps:

When a, the startup of CRT display device, turn-off the line frequency driving pulse that sweep circuit is defeated by line output valve earlier, frequency changer circuit is to described sweep circuit output line frequency driving pulse, minimum line-scanning frequency when its frequency is greater than or equal to described CRT display device operate as normal, described sweep circuit is exported described line frequency driving pulse to the line output valve of described CRT display device;

B, when the power supply of the automatic frequency of described CRT display device sweep test control AFC circuit and frequency dividing circuit reaches steady-working state, described frequency changer circuit is to the line frequency driving pulse of described sweep circuit output normal row sweep frequency.

2, method according to claim 1 is characterized in that, wherein step a specifically comprises:

When a1, the startup of CRT display device, give the register assignment of control line-scanning frequency in the described frequency changer circuit, described frequency changer circuit is exported described line frequency driving pulse to described sweep circuit, the minimum line-scanning frequency when its frequency is greater than or equal to CRT display device operate as normal;

A2, described sweep circuit are exported described line frequency driving pulse to the line output valve of described CRT display device;

3, method according to claim 1 is characterized in that, wherein step b specifically comprises:

The power supply testing circuit of b1, described sweep circuit detects the AFC circuit of described CRT display device sweep test and whether the power supply of frequency dividing circuit reaches steady-working state, if change step b2, otherwise change step a;

B2, described frequency changer circuit progressively are reduced to the normal row sweep frequency with the line frequency driving pulse frequency of its output.

4, method according to claim 1 is characterized in that, wherein step b specifically comprises:

B1, described frequency changer circuit judge whether it reaches the default time to the time that sweep circuit output line frequency driving pulse continues, if change step b2, otherwise change step a;

B2, described frequency changer circuit progressively are reduced to the normal row sweep frequency with the line frequency driving pulse frequency of its output.

5, according to claim 3 or 4 described methods, it is characterized in that wherein step b2 specifically comprises:

Described frequency changer circuit progressively is reduced to the normal row sweep frequency according to step number and the step-length that predefined line frequency changes with described line frequency driving pulse frequency.

6, a kind of system that realizes the CRT soft startup of display device comprises line output valve, it is characterized in that, described system comprises:

Frequency changer circuit, be used in the process that the CRT display device starts the line frequency driving pulse of minimum line-scanning frequency when the sweep circuit output frequency is greater than or equal to CRT display device operate as normal, and be used for after the power supply of the AFC circuit of described CRT display device sweep test and frequency dividing circuit reaches line frequency driving pulse from steady-working state to described sweep circuit output normal row sweep frequency;

Sweep circuit links to each other with described frequency changer circuit, is used for the line frequency driving pulse of described frequency changer circuit input is outputed to line output valve.

7, system according to claim 6, described frequency changer circuit also comprises the register of controlling line-scanning frequency, the value that described frequency changer circuit is composed described register according to system is determined the frequency of the line frequency driving pulse that it is exported.

8, system according to claim 6 is characterized in that, described CRT display device is a CRT monitor.

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