JP2800508B2 - Horizontal deflection circuit - Google Patents

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 of a diode modulator type in a television receiver, a cathode ray display, or the like, which is designed to remove screen disturbance caused by distortion of deflection current.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventionally known diode modulator type horizontal deflection circuit. This circuit is very general, and only the description of the code is described. In FIG. 3, 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a first damper diode, 4 is a second damper diode, 5 is a first resonance capacitor, 6 is a second resonance capacitor, and 7 is a deflection. A coil, 8 is a first scanning capacitor, 9 is a modulation coil, 10 is a second scanning capacitor, 11 is a distortion correction waveform generation / amplitude control circuit, and 1
2 is a flyback transformer. The secondary output of the flyback transformer 12 is rectified by the rectifying element 15 to become a high voltage output, which is supplied to a cathode ray tube (not shown). 1
Reference numeral 3 denotes a power supply Eb applied to one end of the primary winding 14 of the flyback transformer 12, and is supplied to the horizontal output transistor 2 through the primary winding 14. Reference numeral 15 denotes a smoothing capacitor.

When the horizontal deflection circuit is used as a circuit that operates only at a fixed single frequency, the power supply Eb of the above 13 is basically a constant value. Also, the value of the resonance frequency of the first resonance circuit formed by the first resonance capacitor 5 and the deflection coil 7, and the second resonance circuit formed by the second resonance capacitor 6 and the modulation coil 9 It is customary to set the values most suitable for the operation at the fixed single frequency, such as the value of the resonance frequency.

However, when the horizontal deflection circuit is used as a horizontal deflection circuit of a multi-frequency compatible display that can follow a plurality of horizontal frequencies, the value of the deflection coil 7 and the value of the power supply voltage Eb of 13 can be followed. The first and second frequencies are determined so as to be suitable for the upper limit frequency among the frequencies.
Similarly, the frequency of the resonance circuit is generally determined so as to be suitable for the upper limit frequency in the above-mentioned following frequency. After determining in this way, for a plurality of horizontal frequencies lower than the upper limit frequency, the value of the 13 power supply voltage Eb is variably controlled to an appropriate value lower than the value determined by the upper limit frequency, respectively. The horizontal deflection circuit performs a normal frequency tracking operation. Note that a control circuit for linearity correction, high voltage correction and the like is added to the circuit of FIG. 4 for multi-frequency tracking, but is not shown.

[0005]

When the diode modulator type horizontal deflection circuit is used as the horizontal deflection circuit of the display corresponding to the multi-frequency, the current / voltage at the cross point of each operation of two damper diodes, horizontal output transistors, etc. Vertical disturbance noise may be generated on the screen due to distortion of the semiconductor device or a transient phenomenon in the operation of these semiconductor elements. In particular, the device was operated at the lower horizontal frequency within the following frequency where the operation Eb was low. Sometimes, it is noticeable (when Eb is low, it is relatively susceptible to the above-mentioned distortion and transient phenomena), and there is a problem that the image quality of the received image is deteriorated. Therefore, it is necessary to remove the disturbing noise.

FIG. 4 shows one operation waveform of the conventional diode modulator type horizontal deflection circuit shown in FIG. 3. The generation of the noise will be described with reference to FIG.

In FIG. 1, (a) shows the drive voltage applied to the base of the horizontal output transistor 2, (b) shows the deflection current I _Y , (c) shows the collector-ground voltage V _C of the transistor 2, (d) ) Is the collector current I _C , (e) is the first damper current I _D1 , (f) is the second damper current I _D
D2 and (g) show waveforms of the voltage V _M between the intersection B of the two resonance capacitors and the ground. First becomes the first damper current I _{D 1} once zero near the center of the scanning period, but then becomes zero again after flowing slightly in the opposite direction, during which the transistor 2 begins to conduct, the collector of the (d) Although the current I _C starts to flow in the forward direction, the flow of the collector current I _C is small while the reverse current of the damper diode is increasing, and increases more rapidly than when the reverse current passes its peak (portion “a” of d). ). For this reason, at this point, crossover distortion between the damper current and the collector current occurs in the deflection current (portion b) and appears as vertical noise on the image receiving screen.

Also, in the waveform of the drive voltage shown in FIG. 3A, even near the transition from the off period to the on period, the currents of the output transistors, the damper diodes, etc., change transiently due to the mismatch of the operation thereof. As a result, a transient change also occurs in the deflection current I _Y of (b) (b portion b), and one or a plurality of vertical linear noises are generated on the image receiving screen. Note that the distortions at the points A and B, such as the deflection current I _Y and the collector-emitter voltage V _C , are actually very small, but are enlarged in the drawing. (G) is a voltage waveform at the middle point of the diode modulator circuit (point B in FIG. 3), and from the point in time when the drive voltage switches from the off period to the on period, the crossover point between the damper current and the collector current , A transient voltage is generated, and the more the transient voltage rises and falls, the greater the amount of noise generated.

[0009]

As a first means, a parallel circuit of an inductor and a resistor is connected in series with a collector of a horizontal output transistor as a first means. , A second damper diode, and an intersection B of each of the first and second resonance capacitors, the first scanning capacitor, and the modulation coil, an inductor and a resistor, and a high-speed diode. And a third damper diode is connected in parallel with the second resonance capacitor.

[0010]

In the horizontal deflection circuit of the present invention, the transient characteristics of the collector current and the damper current immediately after the drive voltage switches from the off period to the on period are suppressed by the inductor 20 inserted in the collector of the horizontal output transistor 2 ( (Abrupt change is suppressed), and noise at the point of time when the drive voltage changes can be suppressed and removed.

A resistor 21 placed in parallel is an inductor 20
Is for damping, the inductor 20 is a damper current I _D1 (e in FIG. 2) and the collector current I _C (d in FIG. 2)
At the switching point (part a in FIG. 2), on the contrary, the slope of the rise of the collector current acts to be steep and noise is easily generated, so that the action is prevented.
In this way, the inductor 20 and the resistor 21 are integrated to suppress the transient characteristics of the collector current and the damper current immediately after the drive voltage switches from the off period to the on period.

Next, the inductor 22 inserted between the intersection of the first and second damper diodes (A in FIG. 1) and the intersection of the first and second resonance capacitors (B in FIG. 1).
Suppresses a sharp change in the current near (before and after) zero where the damper diode current I _D1 (e in FIG. 2) becomes zero. As a result, the slope of the change in the collector current waveform in the vicinity of the current is reduced, and the damper current is reduced. The generation of noise due to the crossover distortion of the two currents at the point of switching from the current to the collector current is suppressed and eliminated. The resistor 23 is a resistor for damping the inductor 22, suppresses the occurrence of current ringing by the inductor 22, and limits a local increase in the impedance of the inductor 22 locally during the deflection operation. It works to prevent abnormalities in circuit operation. The diode 23 has a function of passing a current unnecessary to the operation of the inductor 22 to pass the current to the first damper diode 3, and the inductor 22 causes ringing in the damper current (particularly when the search is started). (In the vicinity of the rise of the damper current), and prevents the linearity of the current from deteriorating.

The third damper diode 25 plays a role of sharing and flowing a part of the current in the second half of the scan of the second damper diode 4. The third damper diode 25 is a portion where the damper current is switched to the collector current. It acts to suppress and eliminate noise (transient voltage) generated by the inductor 22 in the vicinity where the reverse current of _ID1 passes through the peak and reaches zero.
Further, it has the effect of preventing the linearity of the right part of the image receiving screen from deteriorating.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the horizontal deflection circuit of the present invention will be described with reference to FIG. In FIG. 1, the same reference numerals as those in FIG. 3 indicate the same parts. 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a first damper diode, 4 is a second damper diode, 5 is a first resonance capacitor, 6 is a second resonance capacitor, 7 is a deflection coil, 8 Is a first scanning capacitor, 9 is a modulation coil, 10 is a second scanning capacitor, 11 is a distortion correction waveform generation / amplitude control circuit, 12 is a flyback transformer,
Reference numerals 0 and 22 are inductors, 21 and 23 are resistors, 24 is a high-speed diode, and 25 is a third damper diode. Note that the inductors 20 and 22 may be coils having a value sufficiently smaller than the inductance of the deflection coil 7 (for example,
A so-called bead core in which one copper wire having a required inductor is wrapped with a ferrite core may be used).

Next, the operation will be described. Output transistor 2
The inductor 20 inserted into the collector of the transistor suppresses a sudden change in the collector current and the damper current immediately after the drive voltage applied to the base of the transistor switches from the off period to the on period, and suppresses the deflection coil 7 and the modulation coil 9.
This suppresses the occurrence of distortion in the current and suppresses and eliminates the appearance of linear disturbance noise on the image receiving screen.
In addition, the resistor 21 in parallel with the inductor 20 is provided with a damping circuit for suppressing an adverse effect of current crossover distortion generated at a switching point between the damper current and the collector current (as a side effect) by inserting the inductor 20. It is a resistor.

Next, near the center of the scan after the drive voltage enters the ON period, when the damper current I _D1 and the collector current I _C are switched, a current crossover distortion occurs. When the rate of change of the reverse current is large (therefore, the absolute value of the reverse current is also large), the inductor 2 inserted between A and B in FIG.
Reference numeral 2 reduces the change in the reverse current (as a result, the increase slope of the collector current while the reverse current of the diode 3 flows), thereby suppressing and eliminating the crossover distortion between the damper current and the collector current. The resistor 23 in parallel with the inductor 22 is a resistor for damping. The resistor 23 functions to suppress the occurrence of ringing in the current due to the inductor 22, and the resistor 23 shown in FIG. , B, the impedance of the current path between them is kept low to some extent, thereby suppressing the occurrence of abnormalities in the deflection operation. The high-speed diode 24 has a function of passing a part of the forward current component of the first damper diode 3 by-passing the inductor 22 to suppress the occurrence of ringing in the damper current and to reduce the occurrence of ringing in the inductor 22.
This prevents the rise of the damper current from becoming dull and prevents the linearity of the raster from deteriorating. The third damper diode 25 assists the operation of the second damper diode 4, shares the current flowing in the second half of the scan, and compensates for the second damper diode current in the second half of the search becoming difficult to flow due to the impedance of the inductor 22. Maintains stable operation of the diode modulator circuit, variable amplitude,
The operation is not abnormal even under various operating conditions such as variable frequency. As described above, the inductor 22,
The resistor 23 and the diodes 24 and 25 are integrated, so that the noise can be effectively removed.

FIG. 2 shows one operation waveform of the horizontal deflection circuit of this embodiment of FIG. 1. The collector current I _{C of} FIG. 2D and the damper current I _D1 of FIG. The change in the current of the portion is less gradual than each corresponding portion in FIG.
No abnormal distortion occurs in the collector voltage waveform V _C of (c) and the deflection current waveform I _Y of (b). Also it changes with the rise of the transient voltage waveform in the center part of the midpoint voltage V _M of the diode modulator, falling portion is slowed, hardly out of the noise waveform (g).

[0018]

According to the diode modulator type horizontal deflection circuit, there are two sets of the damper diode and the resonance circuit, and the current path is complicated. Therefore, the crossover distortion due to the mismatch of each circuit current and the influence of the transient characteristics are likely to occur. According to the present invention, it is possible to supply a multi-frequency compatible diode modulator type horizontal deflection circuit which does not generate disturbance noise due to transient characteristics such as a damper current and a collector current and crossover distortion to the image receiving screen with a simple circuit configuration.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing operation waveforms in a circuit according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional horizontal deflection circuit.

FIG. 4 is a diagram showing operation waveforms in a conventional circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horizontal drive circuit 2 Horizontal output transistor 3,4 Damper diode 5,6 Resonant capacitor 7 Deflection coil 8,10 Scanning capacitor 9 Modulation coil 20,22 Inductor 24,25 Diode

Claims (1)

(57) [Claims] A first output terminal of a horizontal output transistor is connected to a first terminal.
, A cathode of a first resonance capacitor, a horizontal deflection coil connected in series, and a first
One end of a first series circuit composed of a scanning capacitor of the above, and one end of the input side of the flyback transformer are connected, respectively, the anode of the first damper diode, the other end of the first resonance capacitor, The other end of the first series circuit is commonly connected to each other, and the common connection point is connected to a cathode of a second damper diode, one end of a second resonance capacitor, a modulation coil connected in series, One end of a second series circuit including a second scanning capacitor is connected to each other, and the anode of the second damper diode, the other end of the second resonance capacitor, and the other end of the second series circuit. And each end is grounded,
A horizontal deflection current control means for applying a predetermined control voltage from one end of the modulation coil so as to control a horizontal deflection current flowing through the horizontal deflection coil to a predetermined value. , A parallel circuit of an inductor and a resistor is connected in series with the collector of the first and second resonance capacitors, and an intersection of an anode of the first damper diode and a cathode of the second damper diode; A parallel circuit of an inductor, a resistor, and a high-speed diode is connected between the intersections of the first scanning capacitor and the modulation coil, and a third damper diode is connected in parallel with the second resonance capacitor. A horizontal deflection circuit, which is connected.