JPH06268881A - Horizontal deflecting circuit - Google Patents

Abstract

PURPOSE:To secure the reliability of a circuit and the stability of pictures by preventing the malfunction of output circuits without giving a large time constant to drive circuits of a horizontal output circuit and a high voltage output circuit. CONSTITUTION:The output of a horizontal oscillation circuit 11 is supplied to the base of a drive transistor TR 31. The collector of the TR 31 is connected to a power terminal 12 through a load resistor 32 and filters 13 and 14 which eliminate a pulse noise. The connection point between the collector of the TR 31 and the resistor 32 is connected to the gate of an output TR 51. The drain of the TR 51 is connected to the power terminal 12 through a primary winding 21a of a flyback transformer 21. A resonance capacitor 38 and a horizontal deflecting coil 40 are provided. The supply voltage of the drive circuit does not rise earlier than that of the oscillation circuit 11, and the malfunction that an excessive current flows to the horizontal output circuit can be prevented. It is unnecessary to give a large time constant to the drive circuit for the purpose of preventing the malfunction, and the stability of pictures is not degraded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal deflection circuit suitable for application to, for example, a flat cathode ray tube.

[0002]

2. Description of the Related Art FIG. 6 shows a flat cathode ray tube (flat CR
T) 1 is shown. In the figure, 1a is a neck portion provided with an electron gun (not shown), 1b is a funnel portion, 1
Reference numeral c is a screen panel, 1d is a front panel, and 1e is a fluorescent screen formed on the screen panel 1c. The screen panel 1c, the front panel 1d, etc. are made of transparent glass. The fluorescent screen 1e is inclined at a relatively small angle with respect to the central axis of the electron gun.
The image displayed on the screen is observed from the front panel 1d side which is substantially perpendicular to the central axis of the electron gun.

In such a flat cathode ray tube 1, keystone distortion (inverse trapezoidal distortion) occurs due to its structure. That is,
The horizontal deflection scanning is performed from the upper part to the lower part of the phosphor screen 1e. However, since the deflection angle θ1 of the upper part and the deflection angle θ2 of the lower part are different, when the horizontal deflection scanning is performed with a constant deflection power (current), it approaches the lower part. As the scanning amplitude decreases, keystone distortion occurs.

In order to correct this keystone distortion, it is necessary to dynamically increase the horizontal deflection current Ipp as the fluorescent screen 1e is scanned from the upper part to the lower part. Here, the power supply voltage eo of the horizontal deflection circuit and the horizontal deflection current Ipp
Has a relationship of eo = Ly (Ipp / Ts) = K.Ipp, where Ly is the inductance of the horizontal deflection coil (H.DY) and Ts is the horizontal scanning period. Here, K = (Ly / Ts). That is, it is understood that the power supply voltage eo needs to be dynamically changed in order to dynamically increase the horizontal deflection current Ipp. In order to realize this, a so-called power supply modulation method in which a power supply voltage is modulated by a sawtooth wave signal having a vertical cycle is generally widely used.

FIG. 7 shows a horizontal deflection circuit and a high voltage generation circuit of a flat cathode ray tube. This example shows a separate type in which the horizontal deflection circuit and the high voltage generation circuit are separated.

In the figure, 11 is a horizontal oscillation circuit.
Reference numeral 12 is a power supply terminal to which a DC voltage + Vcc (for example, + 10V) is supplied. The power supply terminal 12 is grounded through a series circuit of a resistor 13 and a capacitor 14 which form a low pass filter, and the resistor 13 and the capacitor 1 are connected to each other.
Power is supplied to the horizontal oscillation circuit 11 from the connection point P2 of 4.

The horizontal oscillation signal output from the horizontal oscillation circuit 11 is passed through the resistor 15 to the high voltage drive transistor 1
6 bases. The emitter of this transistor 16 is grounded, and its collector is connected to the power supply terminal 12 via the resistor 17. The connection point of the collector of the transistor 16 and the resistor 17 is grounded via the coupling capacitor 18 and the clamping diode 19, and the connection point of the capacitor 18 and the diode 19 is connected to the base of the high voltage output transistor 20.

The emitter of the transistor 20 is grounded,
The collector is the primary winding 2 of the flyback transformer 21.
It is connected to the intermediate tap of 1a. This transistor 20
A resonance capacitor 22 and a damper diode 23 are connected in parallel between the collector and the ground. The power supply terminal 12 is grounded via a series circuit of a coil 24 and a capacitor 25 which form a low pass filter, and the connection point of the coil 24 and the capacitor 24 is a flyback transformer 21.
Is connected to one end of the primary winding 21a.

Further, one end of the secondary winding 21b of the flyback transformer 21 is connected to a high voltage rectifier circuit 26 having a multiple voltage. The high voltage rectifier circuit 26 rectifies the pulse voltage obtained at one end of the secondary winding 21b, and the high voltage HV is applied to the terminal 27.
Is derived. The other ends of the primary winding 21a and the secondary winding 21b of the flyback transformer 21 are connected to each other, and the connection point P1 thereof is grounded via a diode 28 and a capacitor 29 forming a rectifying and smoothing circuit.

The horizontal oscillation signal output from the horizontal oscillation circuit 11 is supplied to the base of the horizontal drive transistor 31 via the resistor 30. This transistor 31
Is grounded, and its collector is connected to the power supply terminal 12 through the resistor 32. The connection point of the collector of the transistor 32 and the resistor 32 is grounded via the coupling capacitor 33 and the clamping diode 34, and the connection point of the capacitor 33 and the diode 34 is connected to the base of the horizontal output transistor 35.

The emitter of the transistor 35 is grounded,
The collector is connected to the diode 28 and the capacitor 2 via the choke coil 36 and the keystone correction circuit 37.
9 connection point P1. Keystone correction circuit 37
Then, in order to correct the above-mentioned keystone distortion, the voltage obtained at the connection point P1 is modulated by a sawtooth wave signal having a vertical period. Further, a series circuit of a resonance capacitor 38, a damper diode 39, a horizontal deflection coil 40 and an S-shaped correction capacitor 41 is connected in parallel between the collector of the transistor 35 and the ground.

In the above structure, since the flat type cathode ray tube has a small deflection power, the horizontal drive transistor 3
1 is a horizontal output transistor 35 with the resistor 32 as a load.
Can drive. For example, in the case of a 4-inch type, since the collector current of the transistor 35 is about 0.7 to 1 A (peak to peak), when the current amplification factor of the transistor 35 is hFE ≧ 100, its base current is about 15 μm.
Get better with mA. Therefore, the resistance value of the resistor 32 can be set to 1.5 kΩ, and the connection point of the collector of the transistor 31 and the resistor 32 and the base of the transistor 35 can be coupled using the capacitor 33.

The horizontal oscillation circuit 11 is generally of VCO type. This circuit has a very high control sensitivity, is prone to malfunction due to disturbance noise, and is particularly susceptible to power supply voltage noise. For example, at a low temperature of about −10 ° C., the capacitance of the electric field capacitors included in the high voltage circuit, the main power source, etc. is drastically reduced, and the power source impedance increases. As a result, pulsed noise from the high-voltage circuit is carried on the power supply line, so that the VCO malfunctions and the oscillation frequency changes, and the AFC circuit (not shown) operates to control the oscillation frequency. Reproduced as image noise (waviness at the top of the vertical line). In order to prevent this, as described above, the low-pass filter composed of the resistor 13 and the capacitor 14 is inserted in the power supply path of the horizontal oscillation circuit 11 so that the VCO does not respond to pulse noise.

When the low-pass filter is inserted in the power supply path of the horizontal oscillation circuit 11 in this way, the horizontal oscillation circuit 11
The power supply voltage rises later than the power supply voltage of the drive circuit and the output circuit, the horizontal oscillation circuit 11 operates later than the drive circuit and the output circuit, and the fuse of the power supply circuit is blown due to malfunction depending on the timing. That is, the transistors 31 and 16 are in the off state until the horizontal oscillation circuit 11 starts up, and the transistor 3
Since 5 and 20 are turned on, an excessive current flows and the fuse is blown.

In order to prevent such a malfunction, it is necessary to make the power supply rise time constant of the drive circuit and the output circuit larger than the power supply rise time constant R1 and C1 of the horizontal oscillation circuit 11. For example, the time constant R of the drive circuit
The time constants R1 and C1 are set so as to satisfy the following expressions with respect to the time constants L and C of L and C2 and the high voltage circuit.

R1 ・ C1 ≦ RL ・ C2 + L ・ C

[0017]

However, increasing the time constant of the drive circuit of the horizontal deflection circuit or the high voltage generation circuit deteriorates the transient response characteristics (switching characteristics) of the transistors 35 and 20, so that stable operation of an image is performed. Has not been resolved at all.

Therefore, in the present invention, the malfunction of the output circuit is prevented without giving a large time constant to the drive circuit of the horizontal output circuit or the high voltage output circuit, and the reliability of the circuit and the stability of the image are improved. Is.

[0019]

In the horizontal deflection circuit according to the first invention, the power supply of the horizontal drive circuit is shared with the power supply of the horizontal oscillation circuit.

In the horizontal deflection circuit according to the second aspect of the present invention, in the horizontal deflection circuit in which power is supplied to the horizontal output circuit from the separately formed high voltage generation circuit, the power source of the drive circuit for driving the high voltage output circuit of the high voltage generation circuit. Is shared with the power supply of the horizontal oscillation circuit.

[0021]

In the first aspect of the present invention, since the power supply of the horizontal drive circuit is shared with the power supply of the horizontal oscillation circuit, even if a low-pass filter is inserted in the power supply path of the horizontal oscillation circuit, the power supply voltage of the horizontal drive circuit is Does not rise earlier than the rise of the power supply voltage of the horizontal oscillation circuit, and it is possible to prevent inconvenience such as excessive current flowing to the horizontal output circuit due to a malfunction and the fuse of the power supply circuit being blown, thus improving the reliability of the circuit. It will be possible. Further, the drive circuit of the horizontal output circuit does not need to have a large time constant in order to prevent malfunction, and the stability of the image is not impaired.

In the second aspect of the invention, since the power source of the drive circuit for driving the high voltage output circuit is shared with the power source of the horizontal oscillation circuit, even if a low-pass filter is inserted in the power supply path of the horizontal oscillation circuit, the high voltage is high. The power supply voltage of the output circuit and the horizontal output circuit does not rise faster than the power supply voltage of the horizontal oscillation circuit, and an excessive current may flow to the high-voltage output circuit and the horizontal output circuit due to a malfunction, causing the fuse of the power supply circuit to blow. Inconvenience can be prevented and the reliability of the circuit can be improved. Further, it is not necessary to give a large time constant to the drive circuit of the horizontal output circuit or the high voltage output circuit in order to prevent malfunction, and the stability of the image is not impaired.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. This example is an example applied to a conventional type in which the high voltage generation circuit and the horizontal deflection circuit are not separated. In FIG. 1, parts corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, the horizontal oscillation signal output from the horizontal oscillation circuit 11 is supplied to the base of a horizontal drive transistor 31 via a resistor 30. The emitter of this transistor 31 is grounded and its collector is resistor 3
It is connected to the connection point P2 of the resistor 13 and the capacitor 14 which form the low-pass filter via 2. The connection point between the collector of the transistor 31 and the resistor 32 is connected to the gate of an N-channel enhancement type MOS field effect transistor 51 that constitutes a horizontal output circuit. The source of the transistor 51 is grounded, and the drain thereof is connected to the other end of the primary winding 21a of the flyback transformer 21. The series circuit of the resonance capacitor 38, the horizontal deflection coil 40, and the S-shaped correction capacitor 41 is connected in parallel between the drain of the transistor 51 and the ground.

This example is constructed as described above, and the other parts are constructed similarly to the example of FIG.

FIG. 2 shows a MOS field effect transistor 51.
The horizontal axis represents the drain-source voltage VDS, and the vertical axis represents the drain current ID. And
A curve a in the figure shows the relationship between the voltage VDS and the current ID (ON characteristic) when the transistor 51 is on, and a curve b shows the relationship between the voltage VDS and the current ID when the transistor 51 is off (diode characteristic). Is shown.

Next, the operation will be described with reference to the waveform chart of FIG.

When the oscillation output as shown in FIG. 3A is supplied from the horizontal oscillation circuit 22 to the base of the transistor 31, a horizontal drive pulse is supplied to the gate of the transistor 51 as shown in FIG.

The operation of the horizontal output circuit is as follows.
3C is a drain current, FIG. 3D is a drain voltage,
E in the figure shows the resonance capacitor current, and F in the figure shows the deflection current.

When a horizontal drive pulse as shown in FIG. 3B is supplied to the gate of the transistor 51, a deflection current (sawtooth wave current) flows through the deflection coil 40 as shown in FIG.

That is, when a positive pulse is supplied to the base of the transistor 51, the transistor 51 is turned on and a current that linearly increases with time flows through the deflection coil 40 (t11 to t12).

Next, when a negative pulse is supplied to the gate of the transistor 51, the transistor 51 is turned off, and the current continues to flow in the same direction due to the inductance inertia to charge the resonance capacitor 38. This charging current decreases with time and the voltage of the resonant capacitor 38 increases. The charging current becomes zero and the voltage (drain voltage) of the resonance capacitor 38 reaches a peak (t12 to t13).

Next, the resonance capacitor 38 is connected to the deflection coil 4
It discharges through 0, the voltage gradually decreases, and the reverse current increases in the deflection coil 40. Resonance capacitor 38
Voltage returns to its original value and the reverse current reaches a peak (t13 to t14).

Next, the transistor 51 conducts as a diode due to the counter electromotive force of the deflection coil 40 (see the diode characteristic of the curve b in FIG. 2), and the current continues to flow in the same direction. The magnitude of the current gradually decreases (t14 to t15). Then, when a positive pulse is supplied to the gate of the transistor 51 to turn on the transistor 51, the transistor 51 is turned on this time (see the characteristic of the curve a in FIG. 2), and the current continues to flow in the same direction. The magnitude of the current gradually decreases to zero (t15 to t16).

Next, since the transistor 51 is turned on, a current that linearly increases with time again flows through the deflection coil 40. A sawtooth current flowing through the deflection coil 40 is formed by the above cycle.

As described above, M is used as the horizontal output transistor.
In the case where the OS field effect transistor 51 is used,
Since the damper diode is unnecessary, the power loss due to the damper diode is eliminated, and the power loss in the horizontal deflection circuit can be reduced. Further, since the MOS field effect transistor 51 is on / off controlled only by applying a voltage to its gate, the drive circuit becomes very simple, and the load resistance can be selected large, so that there is an advantage that power loss can be small.

In this example, the collector of the transistor 31 constituting the horizontal drive circuit is connected to the connection point P2 via the resistor 32, and the power supply of the horizontal drive circuit is the same as the power supply of the horizontal oscillation circuit. Even if a low-pass filter (resistor 13, capacitor 14) is inserted in the power supply path of the horizontal oscillation circuit 11 to remove the pulsed noise, the rise of the power supply voltage of the horizontal drive circuit causes the rise of the power supply voltage of the horizontal oscillation circuit 11. Therefore, it is possible to prevent the inconvenience that an excessive current flows through the horizontal output circuit due to a malfunction and the fuse of the power supply circuit is blown, and the reliability of the circuit can be improved. Further, the drive circuit of the horizontal output circuit does not need to have a large time constant as in the conventional case to prevent malfunction, and the stability of the image is not impaired.

Next, another embodiment of the present invention will be described with reference to FIG. This example is an example applied to a separate type in which a high voltage generation circuit and a horizontal deflection circuit are separated. In FIG. 1, parts corresponding to those in FIGS. 7 and 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, the drain of the MOS field effect transistor 51 forming the horizontal output transistor is connected to the connection point P1 via the choke coil 36 and the keystone correction circuit 37.

The connection point between the collector of the transistor 31 and the resistor 32 is connected to the gate of the enhancement type MOS field effect transistor 52. The source of the transistor 52 is grounded, and the drain thereof is connected to the center tap of the primary winding 21 a of the flyback transformer 21. The resonance capacitor 22 is connected between the drain of the transistor 52 and the ground.

The present example is constructed as described above, and the others are constructed in the same manner as the examples of FIGS. 7 and 1.

In this example, the high voltage output transistor is an MO
It is configured using the S field effect transistor 52, and its operation is similar to that of the horizontal output circuit described above. Since the damper diode is unnecessary, the power loss due to the damper diode is eliminated, and the power loss in the high voltage generating circuit can be reduced. Further, since the MOS field effect transistor 52 is on / off controlled only by applying a voltage to its gate, the drive circuit becomes very simple, and the load resistance can be largely selected, so that there is an advantage that power loss can be small. Therefore, as in this example, the MOS field-effect transistor 5 is composed of only the transistor 31.
Both 1, 52 can be drive-controlled.

In this example, the collector of the transistor 31 constituting the drive circuit of the horizontal deflection circuit and the high voltage generation circuit is connected to the connection point P2 via the resistor 32, and the power source of the drive circuit is the horizontal oscillation circuit. Since it is shared with the power supply, a low-pass filter (resistor 1
3. Even if the capacitor 14) is inserted, the power supply voltage of the drive circuit does not rise faster than the power supply voltage of the horizontal oscillation circuit 11, and an excessive current flows in the horizontal output circuit or the high voltage output circuit due to a malfunction. It is possible to prevent the inconvenience such as the blow of the fuse of the power supply circuit and improve the reliability of the circuit. Further, it is not necessary to give a large time constant to the drive circuit of the horizontal output circuit or the high-voltage output circuit as in the conventional case to prevent malfunction, and the stability of the image is not impaired.

Next, still another embodiment of the present invention will be described with reference to FIG. In this FIG.
The parts corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, a high-voltage drive transistor 1
The collector of 6 is connected to the connection point P2 of the resistor 13 and the capacitor 14 via the resistor 17. The collector of the horizontal drive transistor 31 is connected to the power supply terminal 12 via the resistor 32.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG.

In this example, the collector of the transistor 16 constituting the drive circuit of the high voltage generating circuit is the resistor 1
It is connected to the connection point P2 via 7 and the power supply of the high voltage drive circuit is common to the power supply of the horizontal oscillation circuit. Therefore, in order to remove pulse noise, a low-pass filter ( Even if the resistor 13 and the capacitor 14) are inserted, the power supply voltage of the high-voltage drive circuit does not rise faster than the power supply voltage of the horizontal oscillation circuit 11, and a malfunction causes an excessive current to flow in the high-voltage output circuit, causing the power supply to rise. It is possible to prevent the inconvenience such as the fuse of the circuit from being blown and improve the reliability of the circuit.

In this case, since the power supply of the horizontal output circuit is supplied from the high voltage generation circuit through the keystone correction circuit 37, the horizontal output circuit does not operate until the horizontal oscillation circuit 11 operates, and the horizontal output circuit is erroneously operated. No excessive current flows in the output circuit.

Further, it is not necessary to give a large time constant to the drive circuit of the horizontal output circuit or the high voltage output circuit as in the conventional case in order to prevent malfunction, and the stability of the image is not impaired.

[0050]

According to the first aspect of the invention, since the power source of the horizontal drive circuit is shared with the power source of the horizontal oscillation circuit, even if a low-pass filter is inserted in the power supply path of the horizontal oscillation circuit, the horizontal drive circuit is The power supply voltage rises faster than the horizontal oscillator circuit power supply voltage, and it is possible to prevent inconveniences such as excessive current flowing through the horizontal output circuit due to a malfunction resulting in blown fuses in the power supply circuit. Can be raised. Further, the drive circuit of the horizontal output circuit does not need to have a large time constant in order to prevent malfunction, and the stability of the image is not impaired.

According to the second invention, since the power source of the drive circuit for driving the high-voltage output circuit is shared with the power source of the horizontal oscillation circuit, even if a low-pass filter is inserted in the power supply path of the horizontal oscillation circuit, The power supply voltage of the high-voltage output circuit and the horizontal output circuit does not rise faster than the power supply voltage of the horizontal oscillator circuit, and an excessive current flows through the high-voltage generation circuit and the horizontal output circuit due to a malfunction, causing the fuse of the power supply circuit to be blown. Can prevent the inconvenience of
The reliability of the circuit can be improved. Further, it is not necessary for the drive circuit of the horizontal output circuit or the high-voltage output circuit to have an unnecessarily large time constant in order to prevent malfunction, and the stability of the image is not impaired.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a horizontal deflection circuit according to the present invention.

FIG. 2 is a diagram showing characteristics of a MOS field effect transistor.

FIG. 3 is a diagram showing a waveform of each part of the example of FIG.

FIG. 4 is a connection diagram showing another embodiment of the present invention.

FIG. 5 is a connection diagram showing another embodiment of the present invention.

FIG. 6 is a plan view and a side view showing a flat cathode ray tube (flat CRT).

FIG. 7 is a connection diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 Flat type cathode ray tube 11 Horizontal oscillation circuit 12 Power supply terminal 13, 15, 17, 30, 32 Resistor 14, 18, 25, 29, 33 Capacitor 16 High voltage drive transistor 19, 28, 34 Diode 20 High voltage output transistor 21 Flyback Transformer 22,38 Resonant capacitor 23,39 Damper diode 24 Coil 26 High voltage rectifier circuit 27 Terminal 31 Horizontal drive transistor 35 Horizontal output transistor 36 Choke coil 37 Keystone correction circuit 40 Horizontal deflection coil 41 S-shaped correction capacitor 51,52 MOS field effect transistor

Claims (3)

[Claims] 1. A horizontal deflection circuit characterized in that the power supply of the horizontal drive circuit is common to the power supply of the horizontal oscillation circuit. 2. A horizontal deflection circuit in which power is supplied to a horizontal output circuit from a separately configured high-voltage generation circuit, and the power supply of a drive circuit that drives the high-voltage output circuit of the high-voltage generation circuit is common to the power supply of the horizontal oscillation circuit. A horizontal deflection circuit characterized by: 3. The horizontal deflection circuit according to claim 1, wherein a low-pass filter for removing pulse noise is arranged in a power supply path of the horizontal oscillation circuit.