JP3442800B2 - Flat type CRT - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat CRT having a small screen size and a compact size, and more particularly to a zooming correction technique. 2. Description of the Related Art CRTs include a conventional type in which a high-voltage generating circuit and a horizontal deflection circuit are not separated and a separate type in which these circuits are separated and do not interfere with each other. The conventional type is suitable when the correction amount of the image distortion such as the tall distortion is small, but is not suitable when the correction amount is large because the influence on the high pressure is large. A flat type CRT employs a separate type because the amount of correction for inverted trapezoidal distortion is extremely large. This separate type does not cause the above-mentioned inconvenience because the two circuits do not interfere with each other. However, since the two circuits do not interfere with each other, the so-called zooming development occurs in which the screen size changes because the horizontal deflection voltage is constant even if the high voltage fluctuates depending on the magnitude of the anode current. In order to prevent this zooming phenomenon, a high voltage regulator is generally used. However, since a flat type CRT is a low power consumption and low cost product, a high voltage regulator cannot be used. This was addressed by increasing the amount of overscan. [0005] However, increasing the overscan amount of the beam not only increases the output and the cost but also stabilizes the image. It is an object of the present invention to provide a flat CRT capable of preventing a zooming phenomenon itself without using a high-pressure regulator, minimizing a beam overscan amount and stabilizing an image. Make it an issue. According to a first aspect of the present invention, there is provided a flat type CRT wherein a high voltage generating circuit and a horizontal deflection circuit are separated from each other. The low voltage ΔHV proportional to the anode voltage of
Takes out from the low voltage end of the flyback transformer of the voltage generation circuit
The horizontal deflection is performed by the extracted low voltage ΔHV.
The screen size can be reduced by changing the constant voltage source of the circuit.
The keystone correction is performed . According to the first aspect of the present invention, since the horizontal deflection voltage varies in proportion to the increase or decrease of the anode voltage (high voltage), the beam screen size is kept substantially constant. It is. In addition, the full
Low voltage ΔH taken out from low voltage end of liback transformer
V varies the constant voltage source of the horizontal deflection circuit.
Thus, it is also possible to control at a low output. Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of the present invention. FIG. 1 shows a partial circuit diagram of a flat type CRT. In FIG. 1, a high-voltage generating circuit 1 has a flyback transformer 2, a constant voltage source (+ V _cc ) is connected to one end of a primary side of the flyback transformer 2 and a plurality of times is connected to one end of a secondary side. A pressure rectifier circuit 3 is connected. A transistor 4 is provided at the intermediate tap on the primary side of the flyback transformer 2.
And a base terminal of the transistor 4 is applied with a square wave voltage having a horizontal frequency cycle. In the figure, reference numeral 5 denotes a resonance capacitor, and reference numeral 6 denotes a damper diode. The horizontal deflection circuit 7 has a keystone correction unit 8. The Keaton correction unit 8 has first and second transistors 9 and 10, and a sawtooth voltage having a vertical frequency period is applied to a base terminal of the first transistor 9.
The collector terminal of the first transistor 9 is connected to the base terminal of the second transistor 10. The collector terminal of the second transistor 10 constant voltage source (+ B) is connected, also, the emitter terminal is connected to negative feedback to the base terminal of the first transistor 9 is applied via a resistor R ₁ I have. A voltage e ₀ obtained from the emitter terminal of the second transistor 10 is supplied to a horizontal deflection coil 12 and a transistor 13 via a choke coil 11. A square voltage having a horizontal frequency period is applied to the base of the transistor 13.
, A horizontal deflection current of a sawtooth wave is supplied to the horizontal deflection coil 12. In the drawing, 14 is a resonance capacitor, and 15 is a damper diode. The correction power supply section 16 has a capacitor 17,
One end of the capacitor 17 is connected via a diode 18 to the low voltage end on the primary side of the flyback transformer 2. This capacitor 17 is a flyback transformer 2
, A low voltage ΔHV proportional to the anode voltage HV is charged as shown in FIG. One end of this capacitor 17 is connected to the collector terminal of the first transistor 9 via a resistor _RL ,
Is configured so that a voltage obtained by adding the low voltage ΔHV is applied to the base of the transistor 10. The operation of the above configuration will now be described. In the high-voltage generation circuit 1, when a square wave voltage is applied to the base terminal of the transistor 4, the collector current flows during the beam scanning period, but the collector current of the transistor 4 is suddenly cut off during the flyback period. A large pulse voltage is generated on the secondary side of 2 during the flyback period. This pulse voltage is boosted by the rectifier circuit 3 to produce a high anode voltage H
V (6-7 kV). The anode voltage HV changes depending on the increase or decrease of the anode current. As shown in FIG. 2, the capacitor 17 of the correction power supply unit 16 is charged with the low voltage ΔHV proportional to the anode voltage HV by the pulse voltage. In the horizontal deflection circuit 7, when a sawtooth wave having a vertical frequency cycle is supplied to the base terminal of the first transistor 9 of the keystone correction section 8, a voltage e ₀ modulated by the sawtooth wave is applied to the second transistor. Appears at 10.
When a square wave having a horizontal period is applied to the base terminal of the transistor 13, a horizontal period sawtooth current is supplied to the horizontal deflection coil 12 by turning on / off the transistor 13. The sawtooth current is subjected to vertical period modulation, and the inverted trapezoidal distortion is corrected by this modulation. [0017] The voltage e ₀ of the horizontal deflection circuit 7 relation deflection current I _pp, the inductance of the horizontal deflection coil 12 L _y, if the 1/2 horizontal period duration as shown in FIG. 3, T _s, e _{o = L y · (I pp} / T s) = K · I pp (K = L y / T s:
Constant). Voltage e ₀ is to vary in proportion to Delta] HV, deflection current I _pp varies so as to follow the high-pressure variation (HV + ΔHV). [0018] Here, the equivalent circuit of the keystone correction unit 8 can be represented as shown in FIG. _{4, A = R L / R} E, β = the _{R 2 / (R 1 + R} 2) to the output voltage e _0, e ₀ = a - a _{(e i β e 0) +} ΔHV = {a / (1 + a β)} e i + ΔHV / (1 + a β). Therefore, if the loop gain Aβ is set to a desired value, the beam screen size can be kept substantially constant regardless of the change in the anode voltage. In the case where no negative feedback is given,
E _o when the input was added to 1 / (1 + A β) in order to obtain the same output becomes _{e o = {A / (1} + A β)} · e i + ΔHV. In this embodiment, since ΔHV is the drive voltage of the second transistor 10, the load on the flyback transformer 2 is light, and the pulse rectification of the correction power supply section 16 rectifies a positive pulse equal to the anode voltage. Good followability. As described above, according to the first aspect of the present invention, in a separate flat CRT in which a high-voltage generation circuit and a horizontal deflection circuit are separated, horizontal deflection is performed according to an increase or decrease in anode voltage. Since the voltage level is configured to be variable, the screen size of the beam can be kept substantially constant without using a high voltage regulator, so that the zooming phenomenon can be prevented. As a result, the amount of overscan of the beam can be suppressed to a necessary minimum, and there is an effect that the output can be reduced, the cost can be reduced, and the image can be stabilized to provide high performance and high quality. Also, the low-pressure end of the flyback transformer
From the horizontal deflection circuit by the low voltage ΔHV
Because the constant voltage source is variable, low output control is possible .
There is also the effect that there is.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial circuit diagram of a flat type CRT (Example). FIG. 2 is a characteristic diagram of an anode voltage (HV) and a low voltage (ΔHV) (Example). FIG. 3 is a waveform diagram of a horizontal deflection current (Example). FIG. 4 is an equivalent circuit diagram of a keystone correction unit (embodiment). [Description of Symbols] 1 ... High voltage generation circuit 7 ... Horizontal deflection circuit 9 ... First transistor 10 ... Second transistor 12 ... Horizontal deflection coil 16 ... Correction power supply unit 17 ... Capacitor

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-62-171280 (JP, A)                 JP-A-2-159171 (JP, A)                 JP-A-3-87786 (JP, A)                 JP 47-18215 (JP, A)                 Actual opening 63-49868 (JP, U)                 Actually open 2-38869 (JP, U)                 Tokiko Sho 51-23296 (JP, B2)                 Tokiko Sho 51-4047 (JP, B2)

Claims (1)

(57) Claims 1. A high voltage generating circuit and a horizontal deflecting circuit are separately configured, and a low voltage ΔH proportional to an anode voltage of the high voltage generating circuit is provided.
V is the low voltage of the flyback transformer of the high voltage generation circuit.
The horizontal deflection circuit is taken out from the end by the taken out low voltage ΔHV.
By changing the constant voltage source of the
A flat CRT characterized by performing keystone correction .