JPH05328154A - Deflection circuit - Google Patents

Abstract

PURPOSE:To improve the linearity by providing plural switch circuits and resonance circuits and turning on/off one switch circuit for a period being a half of one period of the resonance frequency of the resonance circuit or below. CONSTITUTION:A 1st switch circuit consists of a field effect transistor (TR) Q1, a diode D1 and a resonance capacitor C, a deflection coil L and a capacitor CS1 form a 1st resonance circuit. Moreover, a 2nd switch circuit consists of a field effect transistor(TR) Q2, a diode D2 and the resonance capacitor C, the deflection coil L and a capacitor CS2 form a 2nd resonance circuit. Then the 1st/2nd resonance circuit supplies a deflection current 1L in a forward/return direction to the coil L. The 1st and 2nd switch circuits repeat on/off operation complementarily and each is operated for a period being a half of one period of the resonance frequency of the resonance circuit or below. Thus, the deflection voltage is biased by the capacitors CS1, 2 to make a change in the deflection current for the forward and return paths equal and then the linearity is improved.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIG. 3) Problem to be Solved by the Invention (FIGS. 4 to 11) Means for Solving the Problem (FIG. 1) Action (FIG. 1) Example (FIG. 1) effect

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection circuit, and is particularly suitable for application to a horizontal deflection circuit for bidirectional deflection.

[0003]

2. Description of the Related Art Conventionally, in this type of deflection circuit, a horizontal deflection coil is driven by using a drive signal whose signal level changes symmetrically before and after a predetermined time point, such as a sine wave signal. A driving deflection circuit (hereinafter referred to as a bidirectional deflection deflection circuit) has been proposed (US Pat. No. 4,6).
72,449).

According to this deflection circuit, scanning from left to right of the screen (hereinafter referred to as forward scanning) and conversely, scanning from right to left of the screen (hereinafter referred to as backward scanning) are performed. Together they can form a display image and reduce the deflection frequency by half. Further, since it is possible to prevent a sharp change in the deflection current such as a sawtooth wave signal, it is possible to reduce unnecessary radiation and the like, and also to reduce the load on the deflection circuit element.

Particularly, if the deflection circuit is formed by a resonance circuit and the deflection coil is driven by a sinusoidal current as shown in FIG.
(A) and (B)), the power required for deflection can be reduced with a simple configuration (Japanese Patent Laid-Open No. 3-72783).

[0006]

However, when a pure sinusoidal current is supplied to drive the deflection coil as described above,
In the period in the vicinity of the peak of the deflection current I _L shown by the diagonal lines in FIG. 3, the linearity is deteriorated, so that the deflection coil must be driven so as to eventually overshoot.
There is a problem that the deflection current I _L is unnecessarily supplied during the shaded period. In practice, when a conventional 34-inch cathode ray tube is used, this period corresponds to about 62% of the whole period, and about 83% of the deflection current I _L in terms of amplitude is wasted. Will be supplied to.

As one method of solving this problem, a method of operating the time axis of the video signal to improve the linearity without supplying a wasteful deflection current I _L can be considered.

However, in this method, the configuration of the video signal processing circuit becomes complicated, and in order to keep the brightness of the entire screen uniform, it is necessary to change the beam current according to the operation on the time axis. The whole structure becomes complicated. Further, there is also a problem that the beam shape and the like change as the beam current changes.

On the other hand, as shown in FIG. 4, a method of forming the deflection current I _L (FIGS. 4 (A) and 4 (B)) so as to delete a useless portion can be considered. In this case, if the deflection coil is driven according to the operation principle shown in FIG. 5, the deflection coil L can be driven by such a deflection current I _L.

That is, the deflection circuit 1 connects the capacitor C1 to the deflection coil L via the selection circuit 2, and the capacitor C1 and the deflection coil L form a resonance circuit. If this state is left as it is, a sinusoidal deflection current flows in the deflection coil L, and if there is no loss in this resonance circuit, this deflection current continuously flows without being attenuated.

With respect to the deflection current I _L thus changing, the deflection circuit 1 selects that the terminal voltage V _L of the deflection coil L (that is, the deflection voltage) falls to a predetermined voltage V _M at time t1. The contact of the circuit 2 is switched to the capacitor C2 side. Here equal the capacitance of the capacitor C1 and C2, and the capacitor C2 that is charged to the voltage -V _M, the deflection voltage V _L is under stood from the voltage V _M at time t1 rapidly to the voltage -V _M is After that, the voltage −V _M changes in a sine wave shape.

The deflection voltage V which changes in a sinusoidal manner in this way
Against _L, the deflection circuit 1 rises to the voltage -V _M at the deflection voltage V _L is subsequently time t2, switch the contacts of the selection circuit 2. As a result, the deflection circuit 1 becomes
Is connected to the capacitor C1 whose terminal voltage is held at the voltage V _M , and the deflection voltage V _L changes from the voltage −V _M to the voltage V _M , and then changes in a sine wave shape.

This results in two capacitors C1 and C2
With connecting alternately switched to the deflection coil L at a predetermined timing, the voltage V _M of the switching, selects the -V _M at a predetermined value, without supplying wasteful deflecting current,
The linearity can be improved.

In practice, this type of deflection current I _L can be generated by the deflection circuit 4 represented by the equivalent circuit in FIG. That is, the deflection circuit 4 forms a resonance circuit with the capacitor C and the deflection coil L via the selection circuit 6.

The deflection circuit 4 in this state, (made during the period that is, from time point t2 in FIG. 4 to time t1) during the period to launch a deflection voltage V _L to or higher than the voltage -V _M, contact of the selection circuit 6 Is switched to insert a DC power source 8 having a voltage of 2V _M into the resonance circuit. Thus during the period from the time point t2 to time point t1, the DC level of the deflection voltage V _L is shifted by a voltage 2V _M, may drive the deflection coil L by the deflection voltage V _L shown in FIG.

Specifically, as shown in FIG. 7, a selection circuit 6 (FIG. 6) is formed by a semiconductor switch with respect to the resonance portion 10 of the condenser C and the deflection coil L, and the energy supply portion 12 is connected. Then, the structure which compensates for the loss of the resonance part 10 can be considered. That is, the deflection circuit 14 connects the series circuit of the field effect transistors Q3 and Q4 in parallel with the DC power supply VB, and the resonance unit 10 via the capacitor C3 and the coil L1 from the connection midpoint of the field effect transistors Q3 and Q4. The drive power source Va is supplied to the.

As shown in FIG. 8, the deflection circuit 14 alternately switches the field effect transistors Q3 and Q4 to the on / off state, and thereby the deflection voltage V _L and the deflection current I of the deflection coil L to be generated. The midpoint voltage Va of the field effect transistors Q3 and Q4 rises in a cycle synchronized with _L (FIGS. 8A and 8B) (FIG. 8C),
Supply power for driving.

Further, the deflection circuit 14 has a series circuit of field effect transistors Q1 and Q2 connected in parallel with the DC power source 8, and the field effect transistors Q1 and Q2 are respectively connected.
Diodes D1 and D2 are connected in parallel with 2. Further, in the deflection circuit 14, the capacitor C is connected to the midpoint of connection between the field effect transistors Q1 and Q2, and the field effect transistors Q1 and Q2 and the diodes D1 and D2 form the selection circuit 6.

As a result, the deflection circuit 14 forms a series resonance circuit of the deflection coil L and the capacitor C by holding the field effect transistor Q2 connected to the ground side in the ON state, and the resonance current is the deflection coil L. On the other hand, by holding the field effect transistor Q2 connected to the DC power source 8 side in the ON state, the DC power source 8 can be inserted in the series resonance circuit of the deflection coil L and the capacitor C. As a result, the deflection circuit 14 can drive the deflection coil L under the conditions described above with reference to FIG. 4 by switching the connection of the selection circuit 6 at the times t1 and t2.

Regarding the switching of the selection circuit 6, in the deflection circuit 14, the connection of the entire selection circuit 6 is switched by controlling the timing of switching the field effect transistors Q1 and Q2 to the off state. That is, the deflection circuit 14 switches the field effect transistor Q2 to the off state when the deflection voltage V _L rises to the voltage −V _M at the time t2 (FIG. 8 (G)). As a result, in the deflection circuit 14, the voltage Vb (FIG. 8 (H)) at the connection midpoint of the field effect transistors Q1 and Q2 is the deflection current I.
_A sudden rise at _L causes the diode D1 to momentarily switch to the ON state (FIG. 8 (D)), and the connection of the switch circuit 6 can be switched from the ground side to the DC power source 8 side.

After the field effect transistor Q1 is turned on in this state, when the deflection voltage V _L falls to the voltage V _M at time t1, the deflection circuit 14 turns off the field effect transistor Q1. Switch (Fig. 8
(E)). As a result, in the deflection circuit 14, the voltage Vb at the connection midpoint of the field effect transistors Q1 and Q2 suddenly falls with the deflection current I _L , and the diode D2 is momentarily switched to the ON state (FIG. 8 (F)). ), The connection of the switch circuit 6 can be switched from the DC power source 8 side to the ground side.

By the way, it can be seen that the DC power supply 8 in this deflection circuit 14 supplies almost no electric power.
That is, in the DC power supply 8, when the diode D1 is switched to the ON state, a current flows through the diode D1. On the contrary, the field effect transistor Q1
Is switched to the ON state and the midpoint voltage Vb starts to drop, the DC power supply 8 turns on the field effect transistor Q.
Current flows out through 1.

When this current value is different between charging and discharging, the change in the deflection current I _L differs between the forward scan and the backward scan, and the displayed image becomes unsightly.

Therefore, as shown in FIG. 9 together with the accompanying circuit, it is considered that the deflection coil L can be driven by the deflection current I _L described above with reference to FIG. 4 even if the DC power source 8 is replaced with the capacitor CS. .. Here, the deflection circuit 20
The voltage detection circuit 22 detects the deflection voltage V _L , and the drive circuit 24 drives the field effect transistors Q3 and Q4 based on the detection result.

The deflection circuit 20 further includes a voltage detection circuit 22.
The detection result of the horizontal sync signal S is output to the AFC circuit 26.
Based on the comparison result of YNC and the voltage detection result, the drive circuit 28 drives the field effect transistors Q1 and Q2, thereby synchronizing the operation of the entire deflection circuit 20 with the horizontal synchronization signal SYNC.

Further, the deflection circuit 20 corrects the pin distortion by connecting the pin distortion correction circuit 30 to the capacitor CS and changing the terminal voltage of the capacitor CS in a parabolic shape in synchronization with the vertical synchronizing signal.

Thus, according to the configuration shown in FIG. 9, linearity can be improved without supplying useless deflection current, and the entire configuration can be simplified by replacing the DC power source 8 with the capacitor CS. Conceivable.

However, in the case of this configuration, there is a problem that the deflection current I _L slightly changes between the forward path and the return path, and there is a problem that the image quality of the display screen deteriorates accordingly. That is, as shown in FIG. 10, the deflection circuit 20 includes a field effect transistor Q1, a diode D1, and a field effect transistor Q2.
And diode D2 are connected to switch circuits 30 and 3 respectively.
It can be replaced with 2 and can be represented by an equivalent circuit.

As can be seen from this equivalent circuit, the deflection circuit 2
0 indicates that when the switch circuit 30 is switched to the on state, the capacitor CS forms a part of the resonance circuit, while the switch circuit 32 is switched to the on state.
The capacitor CS is disconnected from the resonant circuit. As a result, in the deflection circuit 20, the resonance frequency changes between the forward path and the return path, and the deflection current changes in the forward path and the return path.

In this case, as shown in FIG. 11, different display positions are displayed on the forward and backward paths, and the displayed image becomes unreadable. One method of solving this problem is to increase the capacity of the capacitor CS, but if the capacity of the capacitor CS is increased,
It is difficult to correct pin distortion, which is not practical.

The present invention has been made in consideration of the above points, and proposes a deflection circuit capable of effectively avoiding deterioration of image quality and improving linearity without supplying useless deflection current. It is what

[0032]

In order to solve such a problem, in the first invention, a first resonance circuit for supplying a deflection current I _L3 on the outward _path to the horizontal deflection coil L and a deflection current I _L4 on the return _path are provided. A second resonance circuit that supplies the horizontal deflection coil L, and the first resonance circuit includes a first switch circuit 30 that repeats on / off operation at a predetermined timing, a resonance capacitor C, a horizontal deflection coil L, and It is formed of a series resonance circuit with the first DC power supply forming capacitor CS1,
Is a series circuit of a second switch circuit 32 that repeats ON / OFF operations complementary to the first switch circuit 30, a resonance capacitor C, a horizontal deflection coil L, and a second DC power supply forming capacitor CS2. First and second DC power supply forming capacitors CS1 and CS formed by a resonance circuit
2 is selected so that the capacitances are substantially equal, and the first switch circuit 30 has a resonance frequency of 1 of the first and second resonance circuits.
The on / off operation is repeated at a cycle of 1/2 or less of the cycle.

Further, in the second invention, the first switch circuit 30 is formed of a parallel circuit of a first transistor Q1 and a first diode D1, and the second switch circuit 32 is a second transistor Q2 and a second transistor Q2. It is formed by a parallel circuit of the second diode D2.

Further, in the third invention, the first and second
Transistors Q1 and Q2 of the predetermined drive circuit 22,
On / off operation is performed based on the drive signal output from 28, and the drive circuits 22 and 28 output the drive signal based on the voltage V _L at the connection midpoint of the resonance capacitor C and the horizontal deflection coil L.

Further, in the fourth invention, the first and second
The resonance circuit of is a predetermined power supply circuit 2 through a series circuit of a power supply capacitor C3 and a power supply coil L1.
2, 24, VB, Q3, Q4 from the connection midpoint of the resonant capacitor C and the horizontal deflection coil L enter the driving power V _a, the driving power V _a, the first and second switch circuits 3
The signal level switches in synchronization with the ON / OFF operation of 0 and 32.

Further, in the fifth invention, the power supply circuit 2
2, 24, VB, Q3, and Q4 connect the third and fourth transistors Q3 and Q4 in series between the DC power supply VB and the ground, and connect the resonance capacitor C and the horizontal deflection coil L to the voltage V _L at the connection midpoint. As a reference, the third and fourth transistors Q3 and Q4 are alternately turned on and off to drive so that the signal levels are switched in synchronization with the on and off operations of the first and second switch circuits 30 and 32. Generate a power supply V _a .

[0037]

The first resonance circuit that supplies the deflection current I _L3 on the outward _path to the horizontal deflection coil L and the second resonance circuit that supplies the deflection current I _L4 on the return _path to the horizontal deflection coil L are the first and the first resonance circuits, respectively. The two DC power supply forming capacitors CS1 and CS2 are inserted, and the DC power supply forming capacitors CS1 and CS
If the values of 2 are selected to be substantially equal, the changes in the deflection currents I _L3 and I _{L4 on} the forward path and the return _path can be set to be substantially equal to each other, and for one cycle of the resonance frequency of the first and second resonance circuits If the first switch circuit 30 is turned on and off at a cycle of ½ or less, and the second switch circuit 32 is turned on and off so as to change in a complementary manner, no unnecessary deflection current is supplied. , Linearity can be improved.

At this time, the first and second switch circuits 30
And 32 through transistors Q1, Q2 and diode D
If it is formed by a parallel circuit of 1 and D2, this transistor Q
Switch circuit 30 can be easily controlled by turning on and off 1 and Q2.
And 32 can be controlled on and off.

Further, if this on / off control is executed with reference to the voltage V _L at the midpoint of connection between the resonance capacitor C and the horizontal deflection coil L, the switch circuits 30 and 32 can be surely and easily controlled on / off.

[0040] The first and second driving power supply V _a switched is synchronized with the signal level to the on-off operation of the switch circuits 30 and 32, via the series circuit of the power supply capacitor C3 and the power supplying coil L1 , The resonance capacitor C and the horizontal deflection coil L are input to the midpoint of connection, and the first and second
The electric power of the resonance circuit can be supplied.

In this power supply circuit, the third and fourth transistors Q3 and Q4 are connected in series between the DC power supply VB and the ground, and the voltage V _L at the connection midpoint of the resonance capacitor C and the horizontal deflection coil L is used as a reference. , By alternately turning on and off the third and fourth transistors Q3 and Q4, the driving is performed so that the signal levels are switched in synchronization with the on / off operations of the first and second switch circuits 30 and 32 with a simple configuration. The power supply V _a can be generated.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 9 are designated by the same reference numerals, reference numeral 40 denotes a deflection circuit as a whole, a capacitor CS1 is arranged in place of the capacitor CS, and a capacitor CS2 is additionally arranged. ..

That is, in the deflection circuit 40, the capacitors CS1 are connected to the anode side of the diode D1 with respect to the diodes D1 and D2 forming part of the first and second switch circuits, respectively, and the capacitors CS1 are grounded. To do. Further, in the deflection circuit 40, a capacitor SC2 is connected to the cathode side of the diode D2 symmetrically to the capacitor CS1, and the capacitor CS2 is grounded.

As a result, as shown in the equivalent circuit of FIG.
In the deflection circuit 40, the switch circuit 30 (that is, the field effect transistor Q1 and the diode D1), the resonance capacitor C, the deflection coil L, and the capacitor SC1 form a first resonance circuit. The resonance current of the first resonance circuit is output as the deflection current I _L3 of the outward path of the deflection coil L.

On the other hand, the switch circuit 32 (ie, the field effect transistor Q2 and the diode D2).
Is a resonance capacitor C, a deflection coil L and a capacitor S
A second resonance circuit is formed together with C2, and the deflection circuit 40 is
The resonance current of the second resonance circuit is output as the deflection current I _{L4 on} the return path of the deflection coil L.

Here, the deflection circuit 40 includes a capacitor CS1.
And CS2 have substantially the same capacitance, and are set to a small capacitance such that the pin distortion correction circuit can easily correct the pin distortion.

As a result, the deflection circuit 40 can set the frequency of the deflection current I _L to be equal on the forward path and the return path, and can generate the deflection current I _L so as to exhibit the same change on the forward path and the return path.

Therefore, in the deflection circuit 40, the deflection coil L can be driven by this deflection current I _L to effectively avoid the image quality deterioration of the display screen, and thus the transistors Q1 and Q2.
Can be turned off at a predetermined timing to effectively avoid the deterioration of image quality and improve the linearity without supplying useless deflection current.

Further, since the capacitors CS1 and CS2 can be made small in capacity, it is possible to connect a pin distortion correction circuit and correct the screen distortion of the display screen with a simple structure.

According to the above construction, the capacitors having the same capacitance are inserted in the first and second resonance circuits for supplying the deflection currents of the forward path and the backward path to the deflection coil, and the deflection voltage is biased by the capacitors. The change in the deflection current in the forward path and the change in the deflection current in the return path can be held equally, whereby the first and second resonance circuits are switched at a predetermined timing to effectively avoid the deterioration of the image quality and supply the useless deflection current. The linearity can be improved without

Although the switch circuits 30 and 32 are formed of field effect transistors and diodes in the above embodiments, the present invention is not limited to this, and various semiconductor switch circuits and the like are widely applied. be able to.

[0053]

As described above, according to the present invention, the forward and backward deflection currents are supplied to the deflection coil by the first and second resonance circuits, respectively. By biasing the deflection voltage through a capacitor having the same capacity, it is possible to keep the change in the deflection current in the forward path and that in the return path equal with a simple configuration. With this, the first and second resonance circuits are switched at a predetermined timing, the deterioration of the image quality is effectively avoided, and the deflection circuit capable of improving the linearity without supplying useless deflection current is obtained. be able to.

[Brief description of drawings]

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

FIG. 2 is a connection diagram showing an equivalent circuit thereof.

FIG. 3 is a signal waveform diagram for explaining bidirectional deflection.

FIG. 4 is a signal waveform diagram for explaining the improvement of the deflection current.

FIG. 5 is a connection diagram for explaining the operation principle.

FIG. 6 is a connection diagram showing an equivalent circuit of its actual configuration.

FIG. 7 is a connection diagram showing a specific configuration thereof.

FIG. 8 is a signal waveform diagram for explaining the operation.

FIG. 9 is a connection diagram showing a specific deflection circuit including an accompanying circuit.

FIG. 10 is a connection diagram showing an equivalent circuit thereof.

FIG. 11 is a schematic diagram for explaining the deterioration of the image quality.

[Explanation of symbols]

1, 14, 20, 40 ... Deflection circuit, 2, 6, 30, 3
2 ... Switch circuit, C, C1 to C3, CS1, CS2
...... Capacitor, D1 to D4 ...... Diode, L ...... Deflection coil, Q1 to Q4 ...... Field effect transistor.

Claims (5)

[Claims] 1. A first resonance circuit comprising: a first resonance circuit for supplying a forward deflection current to a horizontal deflection coil; and a second resonance circuit for supplying a reverse deflection current to the horizontal deflection coil. Is formed of a series resonance circuit including a first switch circuit that repeats on / off operation at a predetermined timing, a resonance capacitor, the horizontal deflection coil, and a first DC power supply forming capacitor, and the second resonance circuit. Is formed by a series resonance circuit including a second switch circuit that repeats ON / OFF operations complementarily to the first switch circuit, the resonance capacitor, the horizontal deflection coil, and a second DC power supply forming capacitor. The first and second DC power supply forming capacitors are selected to have substantially equal capacities, and the first switch circuit has a resonance frequency of the first and second resonance circuits. Relative period, the deflection circuit and repeating the on-off operation at a cycle of 1/2 or less. 2. The first switch circuit is formed by a parallel circuit of a first transistor and a first diode, and the second switch circuit is formed by a parallel circuit of a second transistor and a second diode. The deflection circuit according to claim 1, wherein the deflection circuit is formed. 3. The first and second transistors are turned on / off based on a drive signal output from a predetermined drive circuit, and the drive circuit is provided at a connection midpoint between the resonance capacitor and the horizontal deflection coil. The deflection circuit according to claim 2, wherein the drive signal is output based on a voltage. 4. The first and second resonance circuits are connected to a middle point of connection of the resonance capacitor and the horizontal deflection coil from a predetermined power supply circuit via a series circuit of a power supply capacitor and a power supply coil. 4. A drive power source is input, and the drive power source switches the signal level in synchronization with the on / off operation of the first and second switch circuits. The deflection circuit described in. 5. The power supply circuit, wherein the third and fourth transistors are connected in series between a DC power supply and a ground, and the third voltage is applied to the resonance capacitor and the horizontal deflection coil as a reference voltage. And the fourth transistor is alternately turned on and off to generate the driving power supply so that the signal level is switched in synchronization with the on and off operations of the first and second switch circuits. The deflection circuit according to item 4.