JPH07283054A - Horizontal high voltage circuit - Google Patents

Abstract

PURPOSE:To protect a high voltage generating circuit by providing a circuit for controlling the switching of a synchronizing signal between an internal oscillation circuit and a high voltage generating circuit asynchronously with an external horizontal synchronizing signal. CONSTITUTION:The horizontal high voltage circuit comprises an internal oscillation circuit 20 generating a horizontal synchronizing pulse Hp' asynchronously with an external horizontal synchronizing signal, a circuit 18 generating a horizontal synchronizing pulse Hp synchronously with horizontal deflection, a circuit 19 for delivering any one of the pulses Hp, Hp' to a high voltage drive circuit 21 based on a high voltage synchronization switching signal EHT received from a CPU 13. The hofizontal high voltage circuit is applicable to a direct view or projection type CRT display corresponding to the continuous horizontal scanning frequency between first and second horizontal scanning frequencies fH1 and fH2 where fH1<fH2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal high voltage circuit of a television receiver which supports a plurality of continuous or discrete horizontal scanning frequencies.

[0002]

2. Description of the Related Art In recent years, in order to improve the image quality of a television receiver, an interlaced signal is made non-interlaced by digital signal processing, and a so-called double-speed scanning compatible television which horizontally drives at a frequency twice the horizontal scanning frequency. Some John receivers have been put to practical use.

In recent years, the practical application of high-definition television, which plays a central role in high-definition television, has made rapid progress, and there are many commercialization cases. However, high-definition is an interlaced system, and there is a trend in the future to seek double-speed scanning of high-definition with the aim of achieving higher image quality, mainly for business purposes.

Further, in the computer market, the demand for higher performance is increasing, and workstations which require a display at a horizontal scanning frequency of around 60 kHz to 70 kHz are occupying a large position.

From the above background, as the direct-view type or projection type CRT display corresponding to the above-mentioned applications, there is a so-called multi-scan type CRT display corresponding to any continuous scanning frequency within a specific scanning frequency range. Mainstream and large in the market. On the other hand, considering high-definition and its double speed, the horizontal scanning frequency is 33.75.
A device specialized for the two-mode horizontal scanning frequency of kHz and 67.5 KHz may also be used in terms of high brightness and high image quality.

Regarding the horizontal high voltage circuit of the direct view type or projection type CRT display corresponding to the two types of the multiple horizontal scanning frequencies, the horizontal deflection circuit and the high voltage generation circuit are of a synchronous type, and the high voltage generation circuit is provided for the horizontal deflection circuit. It can be roughly classified into two types, that is, the asynchronous type. Each of the above two types has advantages and disadvantages, but from the viewpoint of screen noise due to the influence of the high voltage generation circuit, the horizontal deflection circuit and the high voltage generation circuit are synchronously advantageous in principle.

A conventional technique for synchronizing the horizontal deflection circuit and the high voltage generating circuit will be described below with reference to the drawings.

First, the configuration of the conventional example will be described with reference to the block diagram of FIG. The horizontal synchronization signal HD from the outside is input to the horizontal deflection synchronization control circuit 11 and the frequency detection circuit 12. In the frequency detecting circuit 12, the frequency is generally detected by counting the input pulses in a fixed time with a counter, and the detection result is input to the CPU 13. Based on the frequency detection result, the CPU 13 transfers and calculates data to and from the ROM 14 in which the control information is stored in advance for the frequency and the change of the frequency, and the CPU 13 performs the operation according to the detection result.
The horizontal oscillation frequency control circuit 15, the horizontal deflection drive voltage control circuit 16, and the high-voltage drive voltage control circuit 25 output control frequency information and timing signals based on the detected frequency. The horizontal oscillation frequency control circuit 15 outputs the horizontal deflection synchronization control circuit. 11 that controls the self-oscillation frequency of H.11. O
SC is output, and the horizontal deflection drive voltage control circuit 16 outputs a drive voltage control signal H.H.C for controlling the drive voltage of the horizontal deflection output section 17. + B is output, and the high voltage drive voltage control circuit 25 further drives the drive voltage control signal EHT. + B is output. H.
OSC, H.C. + B, EHT. The output timing of each + B depends on the timing signal from the CPU 13. Sync pulse signal HD 'generated by the horizontal deflection sync control circuit 11
Is subjected to waveform shaping and is input to the horizontal deflection output section 17 to flow a sawtooth wave current through the horizontal deflection yoke of the deflection output section 17. In the horizontal deflection output section 17, a pulse voltage is generated in the collector of the output transistor, the pulse voltage is divided by a choke transformer or the like, and the horizontal synchronizing pulse creating circuit 18 outputs the synchronizing pulse Hp. Hp is fed back to the horizontal deflection synchronization control circuit 11 as a return pulse, and the H
D and the AFC circuit built in the horizontal deflection synchronization control circuit 11 perform phase detection and synchronization. Hp is also input to the high-voltage drive circuit 21, and the flyback transformer (hereinafter referred to as FBT) drive circuit 22 and the FBT 23 CR.
A high voltage is applied to the T anode 24. In this case, the FBT 23 of the high voltage generator is always driven at the same frequency as the horizontal scanning frequency in the steady state.

Next, the state transition when the horizontal synchronizing signal HD from the outside changes will be described with reference to FIG. Horizontal scanning frequency fH = 70 kHz, fH = 30 k for simplicity
The case of two frequencies of Hz will be described as an example. First, in the steady state, when fH = 70 kHz, the frequency detection circuit 12
When it is detected that the frequency is 70 kHz, the control signal H.V. OS
C becomes the voltage Va. In addition, the horizontal deflection drive voltage control circuit 1
6 from the horizontal deflection output unit 17 to the control signal H. +
B is the voltage va, and the control signal EHT.V which is output from the high voltage drive voltage control circuit 25 to the FBT drive circuit 22. + B is voltage v
c. Similarly, when fH = 30 kHz, when the frequency detection circuit 12 detects that the frequency is 30 kHz, the horizontal oscillation frequency control circuit 15 causes the horizontal deflection synchronization control circuit 1 to operate similarly.
The control signal H. The OSC becomes the voltage Vb.
Further, the control signal H.V. + B is the voltage vb, and the control signal EHT. + B becomes the voltage vd. Where Va
> Vb and va> vb and vc> vd.

Next, fH is 70 kHz → 30 kHz, 30
State transitions in the two cases of kHz → 70 kHz will be described. fH = 70 kHz → 30 at the timing of ta
When the frequency is changed to kHz, when the change in fH is detected by the frequency detection circuit 12, the H.V. + B changes from va to vb, EH
T. + B changes from vc to vd, and then H.264. OSC is Va
→ Change to Vb. On the contrary, at the timing of tb, fH =
When the frequency changes from 30 kHz to 70 kHz, when the frequency detection circuit 12 detects the change in fH, the H.V. OSC is V
b → Va, and then H.264. + B changes from vb to va, EH
T. + B changes from vc to vd. Here, in the above two state transitions, H.264. OSC and H.M. The timing of + B transition is controlled by a timing signal from each CPU 13 so that the peak value of the collector pulse generated in the output transistor of the horizontal deflection output unit 17 does not become abnormally large and the output transistor is destroyed. Similarly, EHT. + B
At the transition timing of the CPU, the peak value of the collector pulse generated in the output transistor of the FBT drive circuit 22 is not abnormally increased and the output transistor is not destroyed.
It is controlled by the timing signal from 13.

[0011]

However, the conventional techniques shown in FIGS. 5 and 6 have the following problems.

When the horizontal scanning frequency of the horizontal synchronizing signal from the outside is changed, or when the transient period at the time of power-on and power-off is considered, the responsiveness of pulling in the AFC circuit of the horizontal deflection synchronization controller and the transient transition of the power-supply voltage are considered. From the point, the horizontal deflection circuit may operate at an unstable transient frequency during the transition period, and in the high voltage generation circuit driven by the synchronizing pulse from the horizontal deflection circuit, the switching drive element on the primary side of the FBT and FBT is used. There is a risk of overload conditions such as overcurrent and overvoltage. In particular, when the power is turned on and off, the DC voltage supplied to the output section of the high voltage generation circuit is also unstable, and the DC voltage is 1
Considering that the voltage is comparatively high at about 00V to 200V and also large in terms of current, a high voltage generating circuit will be considered in consideration of the case where the condition in which the horizontal scanning frequency of the horizontal synchronizing signal from the outside also changes is overlapped in addition to this condition. The risk to is greater.

The present invention solves the above problems,
When the horizontal scanning frequency of the horizontal synchronizing signal from the outside changes, or when the power is turned on and off, and
In the transient period when various kinds of transient conditions overlap, generation of an overload condition such as overcurrent or overvoltage in the FBT and the switching drive element on the primary side of the FBT in the high voltage generation circuit driven by the synchronous pulse from the horizontal deflection circuit The purpose is to prevent and protect the high voltage generation circuit.

[0014]

In order to solve the above problems, a horizontal high voltage generating circuit according to the present invention first supplies an internal oscillator circuit and a high voltage generating circuit which are internally asynchronous with a horizontal synchronizing signal from the outside. It has a configuration including a high-voltage synchronization signal switching circuit for switching and controlling the synchronization signal, and a power supply control detection circuit for detecting power-on and power-off.

[0015]

According to the present invention, each of the transient periods when the horizontal scanning frequency of the horizontal synchronizing signal from the outside is changed, or when the power is turned on and off and when the two transient conditions are overlapped, is constituted by the above structure. At the FB in the high voltage generating circuit driven by the synchronizing pulse from the horizontal deflection circuit,
It is possible to prevent an overload state such as an overcurrent or an overvoltage from occurring in the switching drive element on the primary side of the T and FBT, and protect the high voltage generation circuit.

[0016]

【Example】

(Embodiment 1) First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a horizontal high voltage circuit according to a first embodiment of the present invention. In FIG. 1, the same parts as those of the conventional example shown in FIG.

In FIG. 1, the difference from the conventional example is that a horizontal sync pulse synchronized with horizontal deflection is generated from an internal oscillator circuit 20 for generating a horizontal sync signal asynchronous with a horizontal sync signal from the outside and a horizontal sync pulse generating circuit 18. Hp and a horizontal synchronizing pulse Hp 'that is asynchronous with the horizontal deflection are input from the internal oscillator circuit 20, and the high voltage synchronizing switching signal EHT.
High voltage synchronous signal switching circuit 1 for outputting either of the synchronous pulses Hp and Hp 'to the high voltage drive circuit 21 by S
9 is added.

The operation of the horizontal high voltage generating circuit in the first embodiment constructed as above will be described. FIG. 2 is a diagram illustrating state transition when the horizontal synchronizing signal HD from the outside changes. As in the case of the description of the conventional example, the horizontal scanning frequency is fH = 70 kHz, fH = for simplicity.
The case of two frequencies of 30 kHz will be described as an example.

First, when fH = 70 kHz in the steady state, when the frequency detection circuit 12 detects that the frequency is 70 kHz, the horizontal oscillation frequency control circuit 15 outputs the control to the horizontal deflection synchronization control circuit 11 via the CPU 13 and the ROM 14. Signal H. The OSC becomes the voltage Va. Further, the control signal H.V.I. output from the horizontal deflection drive voltage control circuit 16 to the horizontal deflection output section 17 is output. + B is the voltage va, and the control signal E output from the high voltage drive voltage control circuit 25 to the FBT drive circuit 22.
HT. + B becomes the voltage vc. Similarly, fH = 30 kHz
In the case of the frequency detection circuit 12, when the frequency detection circuit 12 detects that the frequency is 30 kHz, the horizontal oscillation frequency control circuit 15 outputs the control signal H.H. OSC
Becomes a voltage Vb. In addition, the horizontal deflection drive voltage control circuit 16
The control signal H. + B
Is the voltage vb, and the control signal EHT. Is output from the high voltage drive voltage control circuit 25 to the FBT drive circuit 22. + B is voltage vd
Becomes Where Va> Vb and va> vb and vc> v
d. Further, in the steady state, the high voltage synchronous signal switching circuit 1
9 is High, and in this case, the high-voltage synchronization signal switching circuit 19 outputs the synchronization pulse signal H synchronized with the horizontal deflection.
p is output, and the high voltage generation circuit operates stably at a frequency synchronized with the horizontal deflection circuit.

Next, fH is 70 kHz → 30 kHz, 30
State transitions in the two cases of kHz → 70 kHz will be described. fH = 70 kHz → 30 at the timing of ta
In the case of kHz, when a change in fH is detected by the frequency detection circuit 12, first, EHT. + B changes from vc to vd, and then EHT. S changes from High to Low, and as a result, Hp 'created by the internal oscillation circuit 20 is output from the high voltage synchronization signal switching circuit 19 to the high voltage drive circuit 21, and the high voltage drive circuit 21, the FBT drive circuit 22, and the FBT 23. The high-voltage generating circuit is stably operated at a frequency of Hp 'that is asynchronous with the horizontal deflection. Next, H. + B changes from va to vb, and then H.264. OSC changes from Va to Vb. Through the above state transition, the horizontal deflection synchronization control circuit 11,
After the horizontal deflection circuit composed of the horizontal deflection output unit 14 and the horizontal synchronization pulse generation circuit 15 reaches stable operation at fH = 30 kHz, the EHT. S returns to High, the output synchronizing signal from the high voltage synchronizing signal switching circuit 18 becomes Hp synchronized with the horizontal deflection again, and the high voltage generating circuit operates stably in synchronization with the horizontal deflection circuit.

Conversely, fH = 30k at the timing of tb
In the case of Hz → 70 kHz, when a change in fH is detected by the frequency detection circuit 12, EH is first detected as in the state transition described above.
T. S changes from High to Low, and as a result, Hp 'created by the internal oscillation circuit 20 is output from the high voltage synchronization signal switching circuit 19 to the high voltage drive circuit 21, and the high voltage drive circuit 21, the FBT drive circuit 22, and the FBT 23. The high-voltage generating circuit is stably operated at a frequency of Hp 'that is asynchronous with the horizontal deflection. Next, H. OSC changes from Vb to Va, and then H.S. + B changes from vb to va. After the horizontal deflection circuit including the horizontal deflection synchronization control circuit 11, the horizontal deflection output unit 17, and the horizontal synchronization pulse generation circuit 18 has reached a stable operation at fH = 70 kHz through the above state transition, the EHT. S returned to High, followed by EH
T. + B changes from vd to vc, and high-voltage synchronization signal switching circuit 1
The output synchronizing signal from 9 becomes Hp synchronized with the horizontal deflection again, and the high voltage generation circuit operates stably in synchronization with the horizontal deflection circuit.

The present embodiment is applied to a direct-view type or projection type CRT display corresponding to a continuous horizontal scanning frequency between the first horizontal scanning frequency fH1 and the second horizontal scanning frequency fH2 which are in the relationship of fH1 <fH2. As described above, the first horizontal scanning frequency fH1 is applicable.
It is needless to say that the present invention can be applied even when limited to a direct-view type or projection type CRT display corresponding to a plurality of discrete horizontal scanning frequencies between the second horizontal scanning frequency fH2 and the second horizontal scanning frequency fH2.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram of a horizontal high voltage circuit according to the second embodiment of the present invention. Figure 3
In FIG. 5, the same parts as those of the conventional example shown in FIG.

In FIG. 3, the difference from the conventional example is that a horizontal sync pulse synchronized with horizontal deflection is generated from an internal oscillator circuit 20 for generating a horizontal sync signal asynchronous with a horizontal sync signal from the outside and a horizontal sync pulse generating circuit 18. Hp and a horizontal synchronizing pulse Hp 'that is asynchronous with the horizontal deflection are input from the internal oscillator circuit 20, and the high voltage synchronizing switching signal EHT.
High voltage synchronous signal switching circuit 1 for outputting either of the synchronous pulses Hp and Hp 'to the high voltage drive circuit 21 by S
In addition to the first embodiment in which 9 and 9 are added, a power supply control detection circuit 27 that detects information at power-on and power-off is added.

The operation of the horizontal high voltage circuit according to the second embodiment constructed as above will be described. As is clear from the above description of the configuration, the following operation is performed simultaneously with the operation of the first embodiment.

As shown in FIG. 4, when the power is first turned on at the timing tc in the transient transition state when the power is turned on or off, the power control detection circuit 27 detects the information of the power on and inputs it to the CPU 13. To do. Synchronous switching control signal EH from the CPU 13 to the high voltage synchronous signal switching circuit 19
T. S holds the Low state for a certain period from the initial state, and the high voltage generation circuit synchronizes with the synchronization pulse Hp ′ of the internal oscillation circuit 20. Next, after a lapse of a certain time after the power is turned on, when the power supply control detection circuit 27 detects that all the power supply circuits 26 have stably output the specified voltage at the timing of tc ′, the power supply stability detection information after the power supply is turned on is the CPU 13 Entered in
Next, according to the timing information stored in advance in the ROM 14, a predetermined time after the power is turned on, the EHT. S changes from Low to High, and the high voltage generation circuit and the horizontal deflection circuit operate in synchronization at a stable frequency.

When the power supply cutoff information is detected by the power supply control detection circuit 27 at the timing of td when the power supply is cut off, the CPU 1
3 through the EHT. The state transition of S from High → Low, the high voltage generation circuit becomes stable operation in synchronization with the synchronization pulse Hp ′ from the internal oscillation circuit 20, and then the CPU
Power supply cutoff information is output from 13 to the power supply circuit 26 via the power supply control detection circuit 27, and the power supply is cut off.

In this embodiment, as in the first embodiment, f
The first horizontal scanning frequency fH1 in the relationship of H1 <fH2
, And the second horizontal scanning frequency fH2, the first horizontal scanning frequency fH1 and the second horizontal scanning frequency fH2 have been described as being applicable to a direct view type or projection type CRT display. It is needless to say that the present invention can be applied even when limited to a direct-view type or projection type CRT display corresponding to a plurality of discrete horizontal scanning frequencies between the scanning frequencies fH2.

[0029]

As described above, according to the present invention, when the horizontal scanning frequency of the horizontal synchronizing signal from the outside is changed, or when the power of the television receiver is turned on and off, and the two transient conditions are overlapped. In each transition period of the case, in the high voltage generation circuit driven by the synchronous pulse from the horizontal deflection circuit, the overdrive state such as overcurrent and overvoltage is prevented from occurring in the switching drive element on the primary side of the FBT and FBT, and the high voltage is prevented. The generator circuit can be protected.

[Brief description of drawings]

FIG. 1 is a block diagram of a horizontal high voltage circuit according to a first embodiment of the present invention.

FIG. 2 is a timing explanatory diagram of a horizontal high voltage circuit according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a horizontal high voltage circuit according to a second embodiment of the present invention.

FIG. 4 is a timing explanatory diagram of a horizontal high voltage circuit according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a horizontal high voltage circuit in a conventional example.

FIG. 6 is a timing explanatory diagram of a horizontal high voltage circuit in a conventional example.

[Explanation of symbols]

 11 horizontal deflection synchronization control circuit 12 frequency detection circuit 13 CPU 14 ROM 15 horizontal oscillation frequency control circuit 16 horizontal deflection drive voltage control circuit 17 horizontal deflection output section 18 horizontal synchronization pulse generation circuit 19 high voltage synchronization signal switching circuit 20 internal oscillation circuit 21 high voltage Drive circuit 22 FBT drive circuit 23 FBT 24 CRT anode 26 Power supply circuit 27 Power supply control detection circuit

Claims (2)

[Claims] 1. In a direct-view type or projection type CRT display corresponding to a horizontal scanning frequency between a first horizontal scanning frequency fH1 and a second horizontal scanning frequency fH2 in a relationship of fH1 <fH2, horizontal synchronization from the outside. The internal oscillation circuit for generating a horizontal synchronizing signal asynchronous with the signal is provided, while the frequency detecting circuit for detecting the horizontal scanning frequency from the horizontal synchronizing signal input from the outside and the CPU with the ROM at the output of the frequency detecting circuit. By the processing, first, a horizontal oscillation frequency control circuit for controlling the self-oscillation frequency in the horizontal deflection synchronization control circuit and its switching timing, and secondly, a driving DC voltage for the horizontal deflection output circuit and a horizontal deflection driving voltage for controlling its switching timing. A horizontal synchronizing signal output from the horizontal deflection circuit as a horizontal synchronizing signal supplied to the control circuit and thirdly the high voltage generating circuit. Is provided and a horizontal synchronizing signal from the internal oscillation circuit is supplied, and a high-voltage synchronizing signal switching circuit is provided to change the horizontal scanning frequency of the externally input horizontal synchronizing signal to drive the horizontal deflection circuit. During the transient period when the cycle becomes unstable, the horizontal synchronizing signal to be supplied to the high voltage generating circuit is supplied from the internal oscillating circuit, and during the other steady periods, the horizontal synchronizing signal synchronized to the horizontal deflection circuit is supplied. Horizontal high voltage circuit. 2. In a direct-view type or projection type CRT display corresponding to a horizontal scanning frequency between a first horizontal scanning frequency fH1 and a second horizontal scanning frequency fH2 in a relationship of fH1 <fH2, external horizontal synchronization A frequency detection circuit that detects the horizontal scanning frequency from the externally input horizontal synchronization signal and a power supply control detection circuit that detects power-on and power-off while having an internal oscillator circuit that generates a horizontal synchronization signal that is asynchronous to the signal And a CP with a ROM at the output of the frequency detection circuit and the power supply control detection circuit.
By the processing of U, firstly a horizontal oscillation frequency control circuit for controlling the self-oscillation frequency and its switching timing in the horizontal deflection synchronization control circuit, and secondly, horizontal deflection for controlling the drive DC voltage of the horizontal deflection output circuit and its switching timing. High voltage for switching between the case where the horizontal synchronizing signal output from the horizontal deflection circuit is supplied as the horizontal synchronizing signal supplied to the drive voltage control circuit and the third high voltage generating circuit, and the case where the horizontal synchronizing signal from the internal oscillation circuit is supplied. Equipped with a synchronization signal switching circuit,
Transient period when the horizontal scanning frequency of the horizontal synchronizing signal input from the outside changes and the drive cycle of the horizontal deflection circuit becomes unstable, and the drive cycle of the horizontal deflection circuit at the time of power-on and power-off, the drive condition of the high voltage generation circuit During the transient period when the voltage becomes unstable, the horizontal synchronizing signal to be supplied to the high voltage generating circuit is supplied from the internal oscillation circuit, and during the other steady period, the horizontal synchronizing signal synchronized to the horizontal deflection circuit is supplied. Horizontal high voltage circuit.