JPS63108872A - Horizontal deflecting circuit - Google Patents

Abstract

PURPOSE:To remove the discontinuous part and to have the same inclination in a horizontal deflecting current during an effective scanning period by passing all current passing through a damper diode to a bidirectional switching element. CONSTITUTION:In place of a horizontal deflecting output transistor and the damper diode, a MOSFET 6 as the bidirectional switching element is used. The terminal voltage VC of a capacitor C1 is compared with a reference voltage VS, when the voltage VC exceeds the VS, a signal SC is outputted from a comparator 7. According to the rise of this signal SC, a monostable multivibrator 8 having a time constant tauS is triggered to obtain a pulse P1 of a pulse duration tauS. This pulse P1 and a horizontal driving pulse HD are applied to an OR circuit 9 and this output pulse P2 is applied to the gate electrode of an FET6. Thereby, the difference in the effective scanning period is eliminated to obtain the horizontal deflecting current having to constant inclination.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a horizontal deflection circuit for a television receiver.

[Summary of the invention]

The present invention connects a bidirectional switch, a resonant capacitor, and a horizontal deflection coil in parallel, and compares the voltage at their common connection point with a reference voltage so that the voltage at the common connection point exceeds the reference voltage. A pulse of a predetermined width is generated based on the detection signal, and this pulse and a horizontal drive pulse are supplied to an OR circuit, and the output of the OR circuit controls the bidirectional switching element. By doing so, discontinuity in the horizontal deflection current due to the reverse current of the conventional horizontal output transistor is removed.

[Conventional technology]

FIG. 3 shows a horizontal deflection circuit in a conventional television receiver.

In FIG. 3, one end of a primary coil 2 of a flyback transformer is connected to a terminal 1 to which a 10B power supply is supplied, and a horizontal output transistor 3, A series circuit including a damper diode D, a resonant capacitor CI, a horizontal deflection coil 4, and an S-shaped correction capacitor cm are connected in parallel. A horizontal drive pulse HD is supplied to the base of the transistor 3 from the terminal 5,
Switching of this transistor 3 is controlled.

As shown in FIG. 4, the pulse HD includes a period T including a blanking period in the horizontal scanning period H and a part of the effective scanning period;
It becomes “L” (low level) at T!, which is the majority of the effective scanning period. It is rHJ.

In FIGS. 3 and 4, when pulse HD is "H", transistor 3 is turned on, current I flows from the +B source through coil 2, and horizontal deflection current Iey flows through coil 4, resulting in effective scanning. It will be done. Pulse HD is r
When LJ is reached, transistor 3 is turned off, and the current from the +Bt source charges capacitor C1. This generates a pulse-like voltage vc at the terminal of the capacitor CI,
During the generation period of this vc, a current lay flows in the opposite direction and retrace scanning is performed. After completing this retrace scan, capacitor C
Current to flows from 2 to diode D, and in the middle of this, pulse HD becomes rHJ again, transistor 3 is turned on, currents 1B and lny flow again, and effective scanning is performed.

[Problem that the invention seeks to solve]

In the above-described operation of FIG. 3, the above-mentioned current ■.

Theoretically, all of the current flows through the diode D, and when it becomes approximately zero, the transistor 3 is turned on and is passed on to the current lay during the effective scanning period. However, in reality, if the transistor 3 is turned on while the above-mentioned signal 16 is flowing, this I will be turned on as indicated by the letter "commutation" in FIG.

It has been confirmed that a part of the current is commutated as a reverse current from the emitter to the collector of the transistor 3. - In that case, the threshold voltage v7 of diode D (
Due to the difference between the collector-emitter saturation voltage Vctsat ('qo, 2 V) of the transistor 3 and the collector-emitter saturation voltage Vctsat ('qo, 2 V) of the transistor 3, a step occurs in the voltage vc as shown in FIG. A discontinuous portion with a different slope occurs. This discontinuity causes a television screen to scan faster on the left side of the screen and slower on the right side. This causes a problem in that the left side of the screen becomes darker and the image stretches horizontally, while the right side of the screen becomes brighter and the image shrinks laterally.

This problem is particularly noticeable in picture receivers that use picture tubes that require ultra-precise horizontal linearity, such as index-type color cathode ray tubes, and has been in need of improvement.

[Means for solving problems]

In the present invention, the damper diode D is omitted and a power MO3-FE is used instead of the transistor.
A bidirectional switching element such as T is used. At the same time, the voltage at the common connection point on the power supply side of the bidirectional switch, the resonant capacitor, and the horizontal deflection coil is compared with a reference voltage, and it is determined that the voltage at the common connection point exceeds the reference voltage. A comparison circuit for detecting, a circuit for generating a pulse of a predetermined width based on the detection signal obtained from the comparison circuit, and the pulse and the horizontal driving pulse are supplied, and the output signal drives the bidirectional switching element. A logical sum circuit for control is provided.

[Effect]

Since all of the current flowing through the conventional damper diode can be passed through the bidirectional switching element, the discontinuous portion of the horizontal deflection current mentioned above is removed, and the horizontal deflection current can be made to flow at the same slope during the effective scanning period. Can be done.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and the same parts as those in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, the damper diode D in FIG. 3 is omitted, and the transistor 3 is replaced by a power MO3-FET (hereinafter simply referred to as FET) 6 as a bidirectional switching element. At the same time, the terminal voltage VC of the capacitor C3 and the reference voltage V are compared by the comparator 7, and when VC exceeds V, the comparator 7 outputs a signal Sc that rises to rHJ as shown in FIG. I'm trying to get it. The above V is selected to have a magnitude corresponding to the threshold voltage vT of the damper diode D.

The rise of the signal Sc triggers the monomulti 8 having a time constant τ3, and the monomulti 8 generates a pulse P with a pulse width τ3 as shown in FIG.

get. This pulse P is T of pulse HD as shown in the figure.
The above time constant τ$ is selected so that it overlaps with a part of the 8 periods (“H” period).

Adding this pulse P1 and pulse HD to the OR gate 9,
A pulse P as shown in FIG. 2 is obtained from this OR gate 9, and this pulse P8 is applied to the gate electrode of the FET 6.

According to the above, the pulse P8 becomes rLJ only during the retrace period in which the pulse-like voltage vc is generated, so that the FET 6 is turned off only during this retrace period. As a result, all of the current I. flowing through the conventional damper diode in the first half of the effective scanning period flows in the first half of the ON period of FET 6, and in the second half, the above current ! , and the current with the same slope! . .

flows, so the current 1. in FIG. 4 mentioned above flows. The discontinuous part in can be eliminated.

〔Effect of the invention〕

Discontinuities in horizontal deflection current caused by reverse current in conventional horizontal output transistors can be eliminated. Therefore, the present invention is particularly effective for use in television receivers using picture tubes that require ultra-precise linearity correction, such as index type color cathode ray tubes.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a timing chart for explaining the operation of Fig. 1, Fig. 3 is a circuit diagram of a conventional horizontal deflection circuit, and Fig. 4 is a circuit diagram of a conventional horizontal deflection circuit. 5 is a timing chart for explaining the operation shown in the figure. In addition, in the symbols used in the drawings, 1. coil 6
・−・−・−・−・−−−１−−−・Power MO3-F
ETC3-・・・・・・・・・Resonance capacitor C!
−−−−−−−・−−−1−・−8 character correction capacitor 7
・−・−・−−−−m−−−−−−・Comparator 8
−・・−・・−・−・・・−・・Mono multi 9・−
・・・−・・−・・・・−・−・It is an or gate.

Claims (1)

[Claims] A bidirectional switch element, a resonant capacitor, and a horizontal deflection coil connected in parallel between a power source and a reference potential; a comparison circuit that compares the voltage at a common connection point on the power supply side with a reference voltage and detects that the voltage at the common connection point exceeds the reference voltage; A horizontal deflection circuit comprising: a circuit that generates a pulse; and an OR circuit that is supplied with the pulse and the horizontal drive pulse and controls the bidirectional switch element with its output signal.