JPH06217154A - Horizontal deflecting circuit - Google Patents

Abstract

PURPOSE:To provide the efficient horizontal deflecting circuit by reducing the loss of power. CONSTITUTION:The output side of a horizontal oscillation circuit 22 is directly connected through a predrive circuit 23P to the base of a transistor Q1 of a drive circuit 23, and the collector of the transistor Q1 to provide a horizontal drive pulse is directly connected to the gate of an MOS field effect transistor Q2 of a horizontal output circuit 24. The drain of the transistor Q2 is connected through a primary side coil 32 of an FBT to a power supply terminal +Vcc, and the serial circuit of a resonance capacitor 34, horizontal deflecting coil 35 and S-shaped correction capacitor 36 is connected parallelly between this drain and the ground. Since a current conventionally flowing through a damper diode flows through the transistor Q2, the power loss caused by the damper diode is eliminated. The oscillated output of the horizontal oscillation circuit 22 is transmitted to the transistor Q2 with high fidelity without being distorted by the direct connection configuration, and the switching speed of the transistor Q2 is accelerated.

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 for a television receiver using a flat cathode ray tube (flat CRT).

[0002]

2. Description of the Related Art Conventionally, there is known a flat cathode ray tube in which a fluorescent screen is formed so as to be inclined at a relatively small angle with respect to a central axis of an electron gun. FIG. 4 shows a drive system of this flat cathode ray tube.

In the figure, 1 is a flat cathode ray tube,
K is a cathode electrode, G1 is a first grid electrode, G2 is a second grid electrode forming an accelerating electrode, G3 is a third grid electrode forming a focus electrode, and 2 is a fluorescent screen.
The fluorescent screen has a flyback transformer (hereinafter, “FBT”).
The high voltage HV obtained by rectifying the pulse voltage output by the above is applied.

As the cathode electrode K, unlike the indirectly heated electrode used in a general cathode ray tube, a directly heated electrode which operates at low power and has a quick rising is adopted. A pulse voltage is supplied as a heater voltage 3 from the FBT to the cathode electrode K, and so-called pulse ignition is performed.

In this case, since the FBT winding is connected to the cathode electrode K, the stray capacitance of the cathode electrode K increases, and when the cathode drive system for applying a video signal to the cathode electrode K is adopted, Loss increases. In other words, in order to improve the frequency characteristics, it is necessary to reduce the impedance of the output stage of the video circuit so that the influence of the stray capacitance can be ignored, and the emitter follower configuration or the like will be adopted. Will lead to an increase.

Therefore, a G1 drive system is adopted in which a video signal is applied to the first grid electrode G1 having a relatively small stray capacitance. That is, 4 is an NPN type transistor which constitutes a video amplifier.
The video signal SV is supplied from the terminal 5 to the base of the.
The emitter of this transistor 4 is grounded via a parallel circuit of a resistor 6 and a capacitor 7, and its collector is connected to a power supply terminal + B (for example, 50V) via a resistor 8. Then, the video signal obtained at the connection point of the collector of the transistor 4 and the resistor 8 is applied to the first grid electrode G1 of the cathode ray tube 1 via the capacitor 9.

Voltage source + B1 (for example, 900V)
Is grounded via a series circuit of a variable resistor 10 for focus adjustment, a variable resistor 11 for cutoff adjustment, and a resistor 12. The voltage obtained at the movable terminal of the variable resistor 10 is applied to the third grid electrode G3 of the cathode ray tube 1 via the resistor 13. The mover of the variable resistor 11 is grounded via the capacitor 14, and the voltage obtained at the connection point between the mover and the capacitor 14 is applied to the second grid electrode G2 of the cathode ray tube 1.

Voltage source + B2 (for example, 140V)
Is grounded via a semi-fixed resistor 15 for adjusting the sub-brightness, a resistor 16, a variable resistor 17 for adjusting the brightness and a resistor 18 forming a constant current circuit. The voltage obtained at the mover of the variable resistor 17 is applied to the cathode electrode K via the resistor 19.

The cutoff adjustment of the cathode ray tube 1 is performed by changing the voltage applied to the second grid electrode G2 and the cathode electrode K. That is, the voltage applied to the second grid electrode G2 is varied by the variable resistor 11 to determine the cutoff of the cathode ray tube 1 and the semi-fixed resistor 15
Therefore, the sub-brightness is determined by changing the voltage applied to the cathode electrode K.

As described above, since the voltage applied to the cathode electrode K is changed by the sub-brightness adjustment by the semi-fixed resistor 15 and the brightness adjustment by the variable resistor 17, the resistance value of the resistor 19 is relatively high, for example. 10
It is set to 0 KΩ. However, as is well known, since a beam current proportional to a video signal flows into the cathode electrode K, it is necessary to lower the circuit impedance. Therefore, the cathode electrode K of the cathode ray tube 1 is grounded via the capacitor 20 to reduce the AC impedance.

FIG. 5 shows a configuration of a horizontal deflection circuit of a television receiver using a conventionally known cathode ray tube (including a flat type cathode ray tube). In the figure, the AFC circuit 21
Is supplied with the horizontal synchronizing signal separated from the video signal SV, and the horizontal pulse output from the horizontal output circuit 24 is also supplied to and is compared. The comparison error signal output from the AFC circuit 21 is supplied to the horizontal oscillation circuit 22 as a control signal, and the oscillation output output from the horizontal oscillation circuit 22 is passed through the horizontal drive circuit 23 to the horizontal output circuit 24.
Is supplied to.

FIG. 6 shows a specific configuration of the horizontal output circuit 24. Reference numeral 31 is a horizontal output transistor, and the horizontal drive pulse from the horizontal drive circuit 23 is supplied to the base of the transistor 31. Transistor 31
Is grounded, and its collector is connected to the power supply terminal + Vcc via the primary side coil 32 of the FBT. A series circuit of a damper diode 33, a resonance capacitor 34, a horizontal deflection coil 35, and an S-shaped correction capacitor 36 is connected in parallel between the collector of the transistor 31 and the ground.

Next, the operation of the horizontal output circuit 24 of the example of FIG. 6 will be described with reference to the waveform chart of FIG. A of the same figure shows a horizontal drive pulse, B of the same shows a collector current, C of the same shows a deflection current, D of the same shows a damper current, and E of the same shows a collector voltage.

When a horizontal drive pulse as shown in FIG. 7A is supplied to the base of the transistor 31, a deflection current (sawtooth wave current) flows through the deflection coil 35 as shown in FIG. 7C.

That is, when a positive pulse is supplied to the base of the transistor 31, the transistor 31 is turned on, and a current that linearly increases with time flows through the deflection coil 35 (t1 to t2).

Next, when a negative pulse is supplied to the base of the transistor 31, the transistor 31 is turned off, and the current continues to flow in the same direction due to the inductance inertia to charge the resonance capacitor 34. This charging current decreases with time and the voltage of the resonance capacitor 34 increases. The charging current becomes zero and the voltage of the resonance capacitor 34 reaches its peak (t2 to t3).

Next, the resonance capacitor 34 is connected to the deflection coil 3
5, the voltage gradually decreases, and the reverse current increases in the deflection coil 35. Resonance capacitor 34
Voltage returns to its original value, and the reverse current reaches a peak (t3 to t4).

Next, due to the counter electromotive force of the deflection coil 35, the damper diode 33 becomes conductive, and the current continues to flow in the same direction. The magnitude of the current gradually decreases to zero (t4 to t5).

At this time, since a positive pulse has already been supplied to the base of the transistor 31 and the transistor 31 is on, a current that linearly increases with time again flows through the deflection coil 35. A sawtooth current flowing through the deflection coil 35 is formed by the above cycle.

[0020]

As described above, in the horizontal output circuit 24 shown in FIG. 6, since a part of the sawtooth wave current forming the deflection current flows through the damper diode 33, the power loss in the damper diode 33 is a problem. Has become.

Therefore, it may be considered that the damper diode 33 is not used. In this case, the current flowing through the damper diode 33 will flow through the diode-coupled portion of the base-collector of the transistor 31.

A general power transistor forming the transistor 31 generally has a current amplification factor (hFE = collector current IC / base current IB << 1) in a reverse region due to its structure.
Is so small that it is very difficult to desire transistor operation in this reverse region.

The generally widely used horizontal drive circuit 23 employs a method of driving the transistor 31 by transformer coupling by a drive transformer. In this case, a resistor is inserted between the secondary side of the drive transformer and the base of the transformer 31 so as to supply the optimum base current. When the horizontal deflection current is very small like the flat cathode ray tube shown in FIG.
Coupling is also performed by using a capacitor and a clamping diode instead of the drive transformer.

From the above, when the damper diode 33 is not used as described above, it is not suitable in terms of power loss and scanning linearity.

On the other hand, when the damper diode 33 is not used, it is conceivable to use a power transistor having a built-in damper diode as the horizontal output transistor 31, but there is no solution to the power loss due to the damper diode. In addition, the cost of the transistor 31 is increased.

Therefore, it is an object of the present invention to provide an efficient horizontal deflection circuit with reduced power loss.

[0027]

According to the present invention, in a horizontal deflection circuit of a television receiver using a flat cathode ray tube, a MOS connected in parallel between a power source and a reference potential.
It has a field effect transistor, a resonance capacitor, and a horizontal deflection coil. In a part of the horizontal period, a current in one direction is caused to flow through the MOS field effect transistor to form a part of the sawtooth current flowing through the horizontal deflection coil. In the other part of the horizontal period, a current in the other direction is supplied to the MOS field effect transistor to form another part of the sawtooth current flowing in the horizontal deflection coil.

Further, the output side of the horizontal oscillation circuit is directly connected to the switching element constituting the drive circuit via the pre-drive circuit, and the output side of this switching element is directly connected to the MOS field effect transistor so that the switching element is turned on. At this time, the MOS field effect transistor is turned off, and when the switching element is turned off, the MOS field effect transistor is turned on.

[0029]

In the present invention, the MOS field effect transistor Q2 is used as the switching element of the horizontal output circuit 24, and the current flowing through the conventional damper diode flows through this MOS field effect transistor Q2. Since the horizontal output circuit 24 is configured without using the damper diode, there is no power loss due to the damper diode, and the power loss of the horizontal deflection circuit can be reduced.

The output side of the horizontal oscillation circuit 22 is directly connected to the switching element Q1 constituting the drive circuit 23 via the pre-drive circuit 23P, and the output side of the switching element Q1 is connected to the MOS field effect transistor Q.
By directly connecting to 2, MO can be generated without distorting the oscillation output.
S can be faithfully transmitted to the field effect transistor Q2,
The switching speed of the field effect transistor Q2 can be increased.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIGS. 5 and 6 are designated by the same reference numerals.

In the figure, the horizontal oscillation output from the horizontal oscillation circuit 22 is supplied to the base of an NPN transistor Q3 which constitutes a horizontal predrive circuit 23P.
The base of this transistor Q3 is connected to its emitter via a resistor R1, its collector is connected to the power supply terminal + Vcc via a resistor R2, and its emitter is grounded via a resistor R3.

The connection point between the collector of the transistor Q3 and the resistor R2 is connected to the base of the NPN transistor Q4, the collector of the transistor Q4 is connected to the power supply terminal + Vcc, and the emitter thereof is NPN via the resistor R4. Connected to the collector of the transistor Q5. Also, the emitter of the transistor Q3 and the resistor R
The connection point of 3 is connected to the base of the transistor Q5, and the emitter of this transistor Q5 is grounded.

The connection point between the collector of the transistor Q5 and the resistor R4 is grounded via the resistor R5, and the NPN transistor Q as a switching element which constitutes the horizontal drive circuit 23 via the resistor R6.
1 is connected to the base. The emitter of this transistor Q1 is grounded, and its collector is connected to the power supply terminal + Vcc through the resistor R7.

The connection point between the collector of the transistor Q1 and the resistor R7 is connected to the gate of an N-channel enhancement type MOS field effect transistor Q2 which constitutes the horizontal output circuit 24. The source of the transistor Q2 is grounded and its drain is the primary coil 3 of the FBT.
It is connected to the power supply terminal + Vcc via 2. The resonance capacitor 34, the horizontal deflection coil 35, and the S-shaped correction capacitor 3 are connected between the drain of the transistor Q2 and the ground.
Six series circuits are connected in parallel.

FIG. 2 shows a MOS field effect transistor Q2.
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 Q2 is on, and a curve b shows the relationship between the voltage VDS and the current ID when the transistor Q2 is off (diode characteristic). Is shown.

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

It is assumed that the horizontal oscillation circuit 22 supplies an oscillation output as shown in FIG. 3A to the predrive circuit 23P. When the oscillation output is low level, the transistor Q3 is off, Q4 is on, Q5 is off, the output of the pre-drive circuit 23P is high level, and when the oscillation output is high level, the transistor Q3 is on, Q4 turns off, Q5 turns on, and the output of the pre-drive circuit 23P becomes low level (shown in FIG. 3B).

When the output of the pre-drive circuit 23P goes high, the transistor Q1 turns on,
The output of the drive circuit 23, and hence the horizontal drive pulse supplied to the gate of the MOS field effect transistor Q2, becomes low level, and when the output of the pre-drive circuit 23P becomes low level, the transistor Q1 turns off and the horizontal drive pulse is generated. Becomes high level (Fig. 3C
(Illustrated in).

As described above, when the oscillation output output from the horizontal oscillation circuit 22 is as shown in FIG. 3A, the pre-drive output is as shown in FIG. 3B, and the horizontal drive pulse is as shown in FIG. 3C. Like

Here, when the transistor Q1 is turned on and the horizontal drive pulse is at the low level, the transistor Q2 is turned off, while when the transistor Q1 is turned off and the horizontal drive pulse is at the high level, the transistor Q2 is turned on. It turns on. That is, the transistors Q1 and Q2 operate complementarily. The horizontal oscillation circuit 2
When the oscillating operation of No. 2 is stopped, the oscillating output becomes low level, the transistor Q3 is off, Q4 is on, Q5 is off, Q1 is on, and the transistor Q is off.
2 is off. Therefore, the circuit breakdown due to the transistor Q2 continuing to be turned on is prevented.

Next, the operation of the horizontal output circuit 24 will be described. 3D shows a drain current, FIG. 3E shows a drain voltage, FIG. 3F shows a resonance capacitor current, and FIG. 3G shows a deflection current.

When a horizontal drive pulse as shown in FIG. 3C is supplied to the gate of the transistor Q2, a deflection current (sawtooth current) flows through the deflection coil 35 as shown in FIG.

That is, when a positive pulse is supplied to the base of the transistor Q2, the transistor Q2 is turned on, and a current that linearly increases with time flows through the deflection coil 35 (t11 to t12).

Next, when a negative pulse is supplied to the gate of the transistor Q2, the transistor Q2 is turned off, and the current continues to flow in the same direction due to the inductance inertia to charge the resonance capacitor 34. This charging current decreases with time and the voltage of the resonance capacitor 34 increases. The charging current becomes zero, and the voltage (drain voltage) of the resonance capacitor 34 reaches a peak (t12 to t13).

Next, the resonance capacitor 34 is connected to the deflection coil 3
5, the voltage gradually decreases, and the reverse current increases in the deflection coil 35. Resonance capacitor 34
Voltage returns to its original value and the reverse current reaches a peak (t13 to t14).

Next, due to the counter electromotive force of the deflection coil 35, the transistor Q2 conducts as a diode (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 Q2 and the transistor Q2 is turned on, the transistor Q2 is turned on (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 Q2 is turned on, a current that linearly increases with time again flows through the deflection coil 35. Through the above cycle, a sawtooth wave current flowing in the deflection coil 35 is formed as in the example of FIG.

As described above, in this example, since the MOS field effect transistor Q2 is used as the switching element of the horizontal output circuit 24 and the damper diode is not used, the power loss due to the damper diode is eliminated and the horizontal deflection is eliminated. Power loss in the circuit can be reduced.

The output side of the horizontal oscillation circuit 22 is directly connected to the base of the transistor Q1 of the drive circuit 23 via the pre-drive circuit 23P, and the collector of the transistor Q1 for outputting the horizontal drive pulse is the horizontal output circuit 24. Since it is directly connected to the gate of the MOS field effect transistor Q2, the oscillation output output from the horizontal oscillation circuit 22 is faithfully transmitted to the transistor Q2 without distortion, and the switching speed of the transistor Q2 can be increased.

Although not described above, for example, when a flat cathode ray tube is used, the maximum voltage applied between the drain and source of the MOS field effect transistor Q2 of the horizontal output circuit 24 is about 100 to 150V. There is no problem in terms of pressure resistance.

In the above embodiment, the drain of the MOS field effect transistor Q2 is the primary side coil 32 of the FBT.
Although a so-called convention type connected to the power supply terminal + Vcc via the power supply terminal + Vcc is shown, the drain of the transistor Q2 is connected to the power supply terminal + Vcc via the choke coil.
Needless to say, the present invention can be applied to a so-called separate type connected to Vcc.

[0053]

According to the present invention, the MOS field effect transistor is used as the switching element of the horizontal output circuit, and the current flowing through the conventional damper diode is made to flow through this MOS field effect transistor. Since it is configured without using it, there is no power loss due to it, and it is possible to reduce the power loss of the horizontal deflection circuit.

Further, the output side of the horizontal oscillation circuit is directly connected to the switching element forming the drive circuit via the pre-drive circuit, and the output side of this switching element is directly connected to the MOS field effect transistor forming the horizontal output circuit. As a result, the oscillation output of the horizontal oscillation circuit can be faithfully transmitted to the MOS field effect transistor without distortion.
The switching speed of the MOS field effect transistor can be increased.

[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 a drive system of a flat cathode ray tube.

FIG. 5 is a block diagram showing a configuration of a horizontal deflection circuit.

FIG. 6 is a connection diagram showing a configuration of a horizontal output circuit.

FIG. 7 is a diagram showing waveforms at various points in the example of FIG.

[Explanation of symbols]

 22 horizontal oscillation circuit 23P horizontal pre-drive circuit 23 horizontal drive circuit 24 horizontal output circuit 32 primary coil of flyback transformer 34 resonance capacitor 35 horizontal deflection coil 36 S-shaped correction capacitor Q1 NPN type transistor Q2 N-channel MOS field effect transistor

Claims (2)

[Claims] 1. In a horizontal deflection circuit of a television receiver using a flat cathode ray tube, a MOS field effect transistor, a resonance capacitor, and a horizontal deflection coil connected in parallel between a power supply and a reference potential are provided. In a part of the horizontal period, a current in one direction is passed through the MOS field effect transistor to form a part of the sawtooth current flowing in the horizontal deflection coil, and in the other part of the horizontal period, the MOS field effect is provided. A horizontal deflection circuit characterized in that a current in the other direction is caused to flow through a transistor to form another part of a sawtooth current flowing through the horizontal deflection coil. 2. An output side of the horizontal oscillation circuit is directly connected to a switching element forming a drive circuit via a pre-drive circuit, and an output side of the switching element is directly connected to the MOS field effect transistor, and the switching element is 2. The horizontal deflection circuit according to claim 1, wherein the MOS field effect transistor is turned off when turned on, and the MOS field effect transistor is turned on when the switching element is turned off.