JPH10233937A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate the countermeasure of securing the synthetic capacity of a resonant condenser by using a bipolar transistor high in breakdown strength and low in on-resistance as a resonant condenser changeover switch. SOLUTION: A resonant condenser changeover switch 4 which switches the operation state of a resonant condenser 18 and a diode 60 are connected to the condenser 18. A transistor 24 and a resonant condenser drive circuit 3 form a control circuit that controls the switch 4. When the control circuit and the switch 4 are combined, they operate as a switching circuit for the synthetic capacity of resonant condensers 17 and 18 of a horizontal output circuit 1. That is, the synthetic capacity of the condensers 17 and 18 is automatically switched in accordance with the horizontal frequency of an input signal, and a horizontal interval is adjusted. Further, a bipolar transistor low in on- resistance can be used for the switch 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for selectively receiving a plurality of types of video signals having different horizontal frequencies and generating a horizontal deflection current based on the horizontal frequency of the received video signals.

[0002]

2. Description of the Related Art With the spread of personal computers,
Currently, display devices capable of receiving not only composite video signals such as television broadcasts but also three primary color video signals from a personal computer are being actively developed. For example, Japanese Patent Application Laid-Open No. 61-158271 discloses a display device in which the capacitance of a resonance capacitor in a horizontal deflection circuit is switched in accordance with the horizontal frequency of a received video signal so that various video signals having different horizontal frequencies can be handled. Have been.

In this display device, as shown in FIG. 8, two resonance capacitors connected in parallel to each other are provided, and these are turned on and off by a relay. As a result, the capacitance of the resonance capacitor can be switched.

[0004]

However, in this prior art, since a relay is used for switching the resonance capacitor, a switching sound is generated when the relay is switched. Such a switching sound gives a user of the display apparatus an unpleasant sensation, and is a problem.

As a countermeasure against this, there is a method of using a power MOSFET as a changeover switch of a resonance capacitor.

However, a power MOSFET generally has a larger on-resistance under the same breakdown voltage as compared with a bipolar transistor used for a horizontal output element or the like. The withstand voltage here refers to the withstand voltage on the output side. In the case of a bipolar transistor, it is the rating of the voltage between the collector and the emitter.
This is the rating of the voltage between the sources. The on-resistance is the electrical resistance of the element during conduction, which is the resistance during conduction between the collector and the emitter for a bipolar transistor, and the resistance during conduction between the drain and the source for a power MOSFET. In general, the ON resistance increases as the breakdown voltage increases, and the ON resistance decreases as the breakdown voltage decreases.

Therefore, in order to adapt to the predetermined on-resistance required for switching the resonance capacitor,
A power MOSFET having a low withstand voltage must be used.

When a power MOSFET having a low withstand voltage is used, this power MOSFET cannot be simply replaced with the relay shown in FIG. 8, but first, as shown in FIG. 9, two resonance capacitors are connected in series. It is necessary to connect the midpoint to the drain of the power MOSFET.

However, when two resonance capacitors are connected in series as shown in FIG. 9, the capacitance of each resonance capacitor must be increased as compared with the case where the resonance capacitors are connected in parallel. As the capacitance of the resonance capacitor increases, the shape of the resonance capacitor increases accordingly, leading to an increase in the substrate area.

In view of the above problems, a first object of the present invention is to switch a resonance capacitor without adding an extra circuit which takes up installation space and greatly increases power loss. To provide a display device that can perform the above operations smoothly.

A second object of the present invention is to provide a display device which is effective when an element (for example, a bipolar transistor) other than a power MOSFET is used for a changeover switch of a resonance capacitor.

[0012]

According to one aspect of the present invention for solving the first object, a plurality of types of video signals having different horizontal frequencies are selectively received, and the horizontal frequency of the received video signal is selected. A display device that generates a horizontal deflection current based on a plurality of resonance capacitors connected in parallel to each other to generate the horizontal deflection current, and is connected in series to at least one of the plurality of resonance capacitors. A display device, comprising: a bipolar transistor that switches an operation state of the connected resonance capacitor; and a drive transformer that drives the bipolar transistor based on a horizontal frequency of the received video signal. .

According to one aspect of the present invention for solving the second object, the horizontal frequency of the input signal is detected, and the combined capacitance of the resonance capacitors in the horizontal deflection circuit is determined according to the detected horizontal frequency. A display device for switching, comprising: a detection circuit for detecting a horizontal frequency of the input signal; and a switching circuit for switching the combined capacitance, wherein the detection circuit has at least two levels in accordance with the detected horizontal frequency. When the switching circuit receives one of the two kinds of detection signals, the switching circuit repeats at the detected horizontal frequency, and is included in the horizontal deflection circuit during a period of a fixed length. When the specific resonance capacitor is set in a chargeable / dischargeable state and the other of the two types of detection signals is received, the specific resonance capacitor is thereafter received. Display device is provided, which comprises inhibiting the charge-discharge by capacitor.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a display device according to the present invention will be described.

The overall configuration of the display device of this embodiment is as shown in FIG.

As shown in FIG. 1, the display apparatus receives a normal composite video signal or a digital or analog R, G, B signal and generates a red, green, and blue primary color signal. 54, a cathode ray tube 56 provided with an electron gun that emits an electron beam corresponding to each of the three primary color signals, a horizontal deflection circuit 52 for horizontally deflecting the electron beam in the cathode ray tube 56, and a cathode ray tube 56. It comprises a vertical deflection circuit 55 for deflecting the electron beam in the vertical direction, and a signal processing circuit 51 for directly or processing a signal received from the signal input terminal 50 and sending the processed signal to a target circuit.

Specifically, the signal processing circuit 51 receives a normal composite video signal (a normal TV broadcast reception tuner, a satellite broadcast reception tuner, a composite video signal from a video tape recorder, etc.) via a signal input terminal 50. Signal), the received composite video signal is output to the video circuit 54, the horizontal synchronizing signal and the vertical synchronizing signal are separated from the received composite video signal, and the horizontal synchronizing signal is supplied to the horizontal deflection circuit 52. The signal is given to the vertical deflection circuit 55.

On the other hand, digital or analog R, G, and B signals (R, G, and B signals from some personal computers and double-speed scanning devices that double scanning lines to improve image quality)
G and B signals, for example, are sent to the signal processing circuit 51 in a state where they are separated from the horizontal / vertical synchronization signals, so that the signal processing circuit 51
The G and B signals are output to the video circuit 54 as they are, and the received horizontal / vertical synchronizing signals are output to the horizontal deflection circuit 5 respectively.
2 and output to the vertical deflection circuit 55.

Which video signal the signal processing circuit 51 accepts is determined according to an externally supplied selection signal.

In the case of a composite video signal according to the NTSC system, the vertical frequency is about 60 Hz and the horizontal frequency is about 15.
75 kHz. When a double-speed scanning device is provided, for example, the vertical frequency is about 60 Hz and the horizontal frequency is about 31.5 kHz. On the other hand, in the case of the HDTV system, the vertical frequency is about 60 Hz and the horizontal frequency is about 3 Hz.
3.75 kHz. In some personal computers, the horizontal frequency of the output video signal is about 24 k.
Hz.

As described above, the signal processing circuit 51 can receive various video signals. However, for the sake of simplicity, hereinafter, two composite video signals having the same vertical frequency but different horizontal frequencies will be described. Signals shall be handled.

The horizontal deflection circuit 52 includes a horizontal oscillation circuit 53 that oscillates at the same frequency as the applied horizontal synchronization signal, a horizontal drive circuit 2 that amplifies a pulse signal output from the horizontal oscillation circuit 53, and a horizontal drive circuit 2 A horizontal output circuit 1 driven by the above, and a resonance capacitor drive circuit 3 and a resonance capacitor changeover switch 4 which are characteristic components of the present embodiment.

Although not shown, a frequency-voltage conversion circuit and a comparison circuit are provided before the horizontal oscillation circuit 53. The horizontal synchronizing signal output from the signal processing circuit 51 once enters a frequency-voltage conversion circuit, where it is converted into a voltage signal.
Is output to The horizontal oscillation circuit 53 generates a pulse based on the voltage signal output from the frequency-voltage conversion circuit. Further, the voltage signal output from the frequency-voltage conversion circuit is also input to the comparison circuit. The comparison circuit holds a plurality of voltage values corresponding to each of a plurality of predetermined frequencies as a reference voltage value, compares a given voltage signal with the held reference voltage value, and performs the comparison. From the result, specify the horizontal frequency of the input composite video signal,
A resonance capacitor switching signal is output according to the specified horizontal frequency. The resonance capacitor switching signal will be further described later.

The details of the horizontal deflection circuit 52 are shown in FIG.

As shown in FIG. 1, the horizontal drive circuit 2 adjusts a horizontal drive transformer 13 for forming a base voltage of a horizontal output transistor 15 of the horizontal output circuit 1 and a drive voltage supplied to the horizontal drive transformer 13. It has a resistor 12 and a horizontal drive transistor 14 for driving a horizontal drive transformer 13. In the horizontal drive circuit 2, the ON-OFF method (when the horizontal drive transistor 14 is conducting, the horizontal output transistor 15
Is non-conducting).

The horizontal output circuit 1 comprises a horizontal scanning horizontal deflection coil 19 mounted on a cathode ray tube 56 (see FIG. 1).
An S-shaped capacitor 20 connected in series to the horizontal deflection coil 19; a horizontal output transistor 15 for performing a switching operation for flowing a sawtooth current (horizontal deflection current) through the horizontal deflection coil 19; In combination, resonance capacitors 17 and 18 for causing resonance in the horizontal output circuit 1, a damper diode 16 for damping unnecessary oscillation current generated at the time of resonance, and an AC component of a current supplied from the power supply voltage control circuit 11 And a choke coil 21 for supplying a DC component to the horizontal output circuit 1.

The resonance capacitor 18 is connected to a resonance capacitor changeover switch (specifically, a bipolar transistor) 4 and a diode 60. The resonance capacitor changeover switch 4 is a switch for switching the operation state of the resonance capacitor 18.

When the resonance capacitor changeover switch 4 is closed, the resonance capacitor 18 is incorporated in the horizontal output circuit 1, and the resonance capacitor 18 is ready for charging and discharging.

On the other hand, the resonance capacitor changeover switch 4
Is opened, the resonance capacitor 18 is disconnected from the horizontal output circuit 1, and the resonance capacitor 18 cannot be charged or discharged.

When handling a video signal having a higher horizontal frequency, the resonance capacitor changeover switch 4 is always opened, and the resonance capacitor 18 is separated from the horizontal output circuit 1. In this case, resonance is performed according to the capacitance of the resonance capacitor 17 and the inductance of the horizontal deflection coil 19.

On the other hand, when a video signal having a lower horizontal frequency is to be handled, the resonance capacitor changeover switch 4 is kept open for a certain length of time repeated at the horizontal frequency, and is closed otherwise. deep. That is, when a video signal having a lower horizontal frequency is handled, the resonance capacitor changeover switch 4 is repeatedly opened and closed. Here, the period of a certain length is a period including the horizontal flyback period Thr, and specifically, a period in which Vrb shown in FIG. 4E takes a positive value. The resonance capacitors 17 and 18 are connected to the horizontal output circuit 1
Is not always repeated during the operation of.
The resonance capacitors 17 and 18 execute charging and discharging only during the horizontal retrace period. Therefore, the resonance capacitor changeover switch 4 needs to be closed at least during the horizontal retrace period, but may be open at other times. And
When the resonance capacitor changeover switch 4 is switched as described above, the horizontal output circuit 1 resonates according to the combined capacitance of the resonance capacitors 17 and 18 and the inductance of the horizontal deflection coil 19.

The resonance capacitor switch 4 is operated by the resonance capacitor drive circuit 3. The resonance capacitor drive circuit 3 drives a resonance capacitor drive transformer 29 that forms a base voltage of the resonance capacitor changeover switch 4, a resistor 28 that adjusts a power supply voltage supplied to the resonance capacitor drive transformer 29, and a resonance capacitor drive transformer 29. And a resistor 25, 26 for adjusting a base current flowing through the resonance capacitor drive transistor 27.

In addition to the above, FIG.
3, 24, resistor 22, power supply voltage terminals 5, 7, 8, 1
0, a horizontal oscillation pulse input terminal 6, and a resonance capacitor switching signal input terminal 9 are also shown. Power supply voltage terminal 5,
Reference numerals 7 and 8 are connected to a power supply voltage control circuit (not shown). The horizontal oscillation pulse input terminal 6 is connected to a horizontal oscillation circuit 53
This is a terminal for inputting a pulse (horizontal oscillation pulse Vosc) output from. The resonance capacitor switching signal input terminal 9 is a terminal for inputting the resonance capacitor switching signal output from the above-described comparison circuit. The resistor 22 is a resistor for extracting a change in the collector current of the transistor 23 as a voltage signal. The transistor 23 is a transistor that operates based on the horizontal oscillation pulse Vosc obtained through the input terminal 6. The transistor 24 is a transistor that operates based on a resonance capacitor switching signal obtained via the input terminal 9.

The transistor 24 and the resonance capacitor drive circuit 3 play a role of a control circuit for controlling the resonance capacitor switch 4. The combination of this control circuit and the resonance capacitor changeover switch 4 functions as a circuit for switching the combined capacitance of the resonance capacitors of the horizontal output circuit 1.

Next, the operation of the display device of the present invention will be described. Here, of the two types of composite video signals described above, the composite video signal having the higher horizontal frequency is handled. In accordance with this, it is assumed that the resonance capacitor changeover switch 4 is in the open state.

First, the operation of the horizontal drive circuit 2 and the horizontal output circuit 1 will be described.

In FIG. 2, the horizontal drive circuit 2 inverts and amplifies the horizontal oscillation pulse Vosc input from the horizontal oscillation pulse input terminal 6 to generate a square wave voltage, and applies this to the base of the horizontal output transistor 15. ing. The horizontal output transistor 15 to which the square wave voltage is applied,
By turning on / off the collector current flowing into itself, resonance is generated by the horizontal deflection coil 19 and the resonance capacitor 17. An excess current among the currents generated by the resonance is damped by the damper diode 16.

The above operation will be further described with reference to FIG. FIG. 3A shows the waveform of the horizontal oscillation pulse Vosc. FIG. 3B shows a waveform of the collector voltage Vcp of the horizontal output transistor 15. FIG.
(C) shows the waveform of the horizontal deflection current Idy flowing through the horizontal deflection coil 19.

Period t1 to t2: In this period, the horizontal output transistor 15 is in a conductive state. As a result, the horizontal deflection current Idy gradually starts flowing through the horizontal deflection coil 19, and electromagnetic energy is accumulated.

Period t2 to t3: At time t2, the horizontal output transistor 15 is turned off. Therefore, the horizontal deflection current Id flowing through the horizontal deflection coil 19 is
y flows into the resonance capacitor 17, and at time t3, the above-described electromagnetic energy is converted into electrostatic energy.

Period t3 to t4: In this period, the electric charge stored in the resonance capacitor 17 is discharged via the horizontal deflection coil 19, and the above-mentioned electrostatic energy is converted into electromagnetic energy.

Period t4 to t5: During this period, the damper diode 16 is driven by the back electromotive force of the horizontal deflection coil 19.
Are conducted, and the above-described electromagnetic energy returns to the S-shaped capacitor 20. As a result, the horizontal deflection current Idy flowing through the horizontal deflection coil 19 via the damper diode 16 decreases and becomes 0 at time t5.

By repeating the above operation, the horizontal deflection current Idy has a sawtooth waveform as shown in FIG. The horizontal deflection current Idy generates an electromagnetic wave when flowing through the horizontal deflection coil 19, and deflects the electron beam in the horizontal direction.

The horizontal flyback period T shown in FIG.
The length of hr is determined by the resonance frequency based on the capacitance of the resonance capacitor 17 and the inductance of the horizontal deflection coil 19. Here, the smaller the combined capacitance of the resonance capacitors included in the horizontal output circuit 1, the higher the resonance frequency and the shorter the horizontal flyback period. Conversely, the larger the combined capacitance of the resonance capacitors, the lower the resonance frequency and the longer the horizontal retrace period.

Next, the operation of the resonance capacitor drive circuit 3 and the resonance capacitor changeover switch 4 will be described.

When processing a composite video signal having a higher horizontal frequency, the above-described comparison circuit continues to output a high-level (H-level) resonance capacitor switching signal to the transistor 24. The transistor 24 is turned on while receiving the resonance capacitor switching signal at the H level. During this time, the resonance capacitor switch 4 is maintained in the off state. The waveform of the voltage Vrb on the input side of the resonance capacitor changeover switch 4 is shown in FIG. The waveform of the voltage Va on the output side of the resonance capacitor changeover switch 4 is shown in FIG. When the resonance capacitor changeover switch 4 is in the off state,
No current flows through the resonance capacitor changeover switch 4 and the diode 60, and the potential difference between both ends of the resonance capacitor 18 becomes zero. That is, at the time of resonance, the resonance capacitor 18
, No charge / discharge current flows, and only the resonance capacitor 17 performs charge / discharge.

The above is the operation of the display device when the composite video signal having the higher horizontal frequency is handled. When the video signal having the lower horizontal frequency is handled, the above-described comparison circuit operates to The low-level (L-level) resonance capacitor switching signal is continuously output. The transistor 24 is turned off while receiving the L-level resonance capacitor switching signal. Therefore, the inverted signal of the horizontal oscillation pulse Vosc obtained through the transistor 23 is directly input to the resonance capacitor drive transistor 27. The waveform of the horizontal oscillation pulse Vosc is shown in FIG.

The resonance capacitor drive transistor 27 that has received the inverted signal of the horizontal oscillation pulse Vosc adjusts the resonance capacitor drive transformer 2 according to the inverted signal.
9 is driven. As a result, a drive pulse is output from the resonance capacitor drive transformer 29, and the resonance capacitor changeover switch 4 performs a switching operation in accordance with the drive pulse. The waveform of the voltage Vrb on the input side of the resonance capacitor changeover switch 4 is shown in FIG.
Is shown in The waveform of the voltage Va on the output side of the resonance capacitor changeover switch 4 is shown in FIG. When the resonance capacitor changeover switch 4 is in the ON state (that is, when the voltage Vrb indicates a positive value), the current path from the resonance capacitor 18 to the resonance capacitor changeover switch 4 and the current from the diode 60 to the resonance capacitor 18 Is established, and the resonance capacitor 18
Can be charged and discharged. The horizontal retrace period Thr when the resonance capacitors 17 and 18 perform charging and discharging is shown in FIG.
Is shown in As can be seen from comparison with FIG. 3B, the horizontal retrace period Thr is longer when the horizontal frequency is low, and is shorter when the horizontal frequency is high.

The state of Vcp of the horizontal output circuit 1 is also
This is shown in FIG. FIG. 4C shows a waveform of the horizontal deflection current Idy flowing through the horizontal deflection coil 19. The operation of the horizontal output circuit 1 is the same as that in the case where the horizontal frequency is high except that the resonance capacitor 18 performs charging and discharging, and thus the description is omitted.

As described above, according to the display device of the present embodiment, the combined capacitance of the resonance capacitors is automatically switched according to the horizontal frequency of the input signal, and the horizontal retrace period is adjusted. Although not particularly described, the maximum collector voltage and the like of the horizontal output circuit 1 are set to appropriate values by switching the combined capacitance of the resonance capacitors.

Further, according to the display device of the present embodiment, a bipolar transistor having a smaller on-resistance than a power MOSFET can be used for the resonance capacitor changeover switch. The withstand voltage of the bipolar transistor may be the same as that of the horizontal output transistor 15, for example.

In this embodiment, the bipolar transistor is driven by a transformer. If a transformer is used to drive the bipolar transistor, the bipolar transistor can be driven with lower loss than when the bipolar transistor is driven by a DC amplifier circuit or the like.
As a result, the power consumption of the circuit can be reduced.

As described above, the resonance capacitor drive transistor 27, the resonance capacitor drive transformer 29, and the resonance capacitor changeover switch 4 perform the switching operation (opening / closing operation) only when the horizontal frequency is low.
I do.

Therefore, as the resonance capacitor drive transistor 27 and the resonance capacitor changeover switch 4, relatively low-rated elements having a lower switching speed than the horizontal drive transistor 14 and the horizontal output transistor 15 can be used. Also for the resonance capacitor drive transformer 29, relatively low-rated components having an operating frequency lower than that of the horizontal drive transformer 13 can be used.

Further, in this embodiment, the resonance capacitor drive circuit 3 is provided independently of the horizontal drive circuit 2. In this case, regardless of the design situation of the horizontal drive circuit 2, the resonance capacitor changeover switch 4
Optimum drive conditions can be set.

Next, another embodiment of the display device according to the present invention will be described.

Note that the components used in the above-described embodiments are denoted by the same reference numerals and description thereof may be omitted.

The display device of the present embodiment is a type of display device in which the horizontal deflection current is amplitude-modulated by a vertical parabolic wave using a diode modulation method, and the right and left pincushion distortion generated in the cathode ray tube is corrected. The invention is also applicable to such types of display devices. The overall configuration of the display device is as shown in FIG.

The configurations of the horizontal drive circuit 2 and the resonance capacitor drive circuit 3 are the same as those of the above-described embodiment, and therefore the description thereof is omitted.

The horizontal output circuit 1 includes the basic circuits (horizontal output transistor 15, horizontal deflection coil 19, resonance capacitors 32 and 34, horizontal deflection coil 19, damper diode 30, and S-shaped capacitor) used in the above-described embodiment. 36), a modulation coil 37 connected in series with the horizontal deflection coil 19 via an S-shaped capacitor 36, a resonance capacitor 33 forming a resonance circuit with the modulation coil 37,
35, an S-shaped capacitor 38 for generating a voltage for controlling a horizontal deflection current flowing through the horizontal deflection coil 19,
It comprises a damper diode 30 and a modulation diode 31 connected in series. The horizontal size control circuit 48 controls the voltage between both ends of the S-shaped capacitor 38 based on a control signal (specifically, a signal whose amplitude changes in a parabolic manner with a vertical cycle) provided to an input terminal 49.

The horizontal output circuit 1 is also provided with a flyback transformer 39 and a diode 40, which are sources of an anode voltage supplied to the cathode ray tube. The anode voltage generated through the flyback transformer 39 and the diode 40 is output to the cathode ray tube via the anode voltage output terminal 41.

In the horizontal output circuit 1 having such a configuration, the horizontal deflection coil 19 and the resonance capacitor 32
34 (or the resonance capacitor 34 alone), the modulation coil 37 and the resonance capacitors 33, 3
5 (or the resonance capacitor 35 alone) while operating simultaneously, and using the horizontal size control circuit 48, the amplitude of the voltage between both ends of the S-shaped capacitor 38 is parabolically changed in a vertical cycle. If it is changed, the amplitude of the horizontal deflection current also changes in a parabolic manner in the vertical cycle, and the pincushion distortion of the screen is corrected.

When the DC voltage component of the horizontal size control signal sent to the horizontal size control signal input terminal 49 is adjusted,
The amplitude of the horizontal deflection current changes, and the horizontal size of the screen changes accordingly.

In the horizontal output circuit 1 according to the present embodiment, the resonance capacitors 32 and 33 do not perform charging and discharging when the horizontal frequency is high, but perform charging and discharging when the horizontal frequency is low.

The switching of the resonance capacitors 32 and 33 is as follows.
Resonant capacitor changeover switch 42 and power MOSFET 4
5 at the same time. A diode 47 having the same function as the diode 60 in FIG. 2 is connected between the resonance capacitor 32 and the resonance capacitor switch 42. As can be seen from the configuration of the horizontal output circuit 1, the modulation voltage Vm is smaller than the collector voltage Vcp of the horizontal output transistor 15 (for example, the voltage Vc).
(approximately 、 of p), so that even if the power MOSFET 45 is used to switch the resonance capacitor 33, no particular problem occurs in terms of withstand voltage and on-resistance.

The resonance capacitor switch 42 is
As in the previous embodiment, the resonance capacitor drive circuit 3
Drives. In the power MOSFET 45, the transistor 43 is driven based on the resonance capacitor switching signal input from the resonance capacitor switching signal input terminal 9. The power MOSFET 45 is always on when the horizontal frequency is low, and is always off when the horizontal frequency is high.

The power MOSFET 45 may perform a switching operation similar to that of the resonance capacitor changeover switch 42 (a switching operation of a horizontal cycle that is turned on at least during a horizontal flyback period). Further, a bipolar transistor may be used in place of the power MOSFET 45, and the bipolar transistor may be driven by a circuit similar to the resonance capacitor drive circuit 3.

Next, the operation of the display device of the present invention will be described. Here, of the two types of composite video signals described above, the composite video signal having the higher horizontal frequency is handled, and the resonance capacitors 32, 3
It is assumed that each changeover switch of No. 3 is open.

First, referring to FIG. 6, the horizontal drive circuit 2
The operation of the horizontal output circuit 1 will be described.

Period t1 to t2: In this period, the horizontal output transistor 15 conducts, the horizontal deflection current Idy gradually flows through the horizontal deflection coil 19, and the first electromagnetic energy is accumulated. On the other hand, the modulation current Im gradually flows through the modulation coil 37, and the second electromagnetic energy is accumulated.

Period t2 to t3: At time t2, the horizontal output transistor 15 is turned off, so that the horizontal deflection current Idy flowing through the horizontal deflection coil 19 flows into the resonance capacitor 34, and at time t3, the above-mentioned first deflection current Idy
Is converted into first electrostatic energy. On the other hand, the modulation current Im flowing through the modulation coil 37
Flows into the resonance capacitor 35, and at time t3, the above-described second electromagnetic energy is converted into second electrostatic energy.

Period t3 to t4: In this period, the electric charge stored in the resonance capacitor 34 is discharged via the horizontal deflection coil 19, and the above-described first electrostatic energy is converted into first electromagnetic energy. Also, during this period, the accumulated charge in the resonance capacitor 35 is discharged via the modulation coil 37,
The above-mentioned second electrostatic energy is converted into second electromagnetic energy.

Period t4 to t5: In this period, the damper diode 30 conducts due to the back electromotive force of the horizontal deflection coil 19, and the above-mentioned first electromagnetic energy returns to the S-shaped capacitor 36. As a result, the horizontal deflection current Idy flowing through the horizontal deflection coil 19 via the damper diode 30
Decreases and becomes 0 at time t5. In this period, the back electromotive force of the modulation coil 37 causes the damper diode 31 to conduct, and the above-described second electromagnetic energy returns to the S-shaped capacitor 38. As a result, the modulation current I flowing through the modulation coil 37 via the damper diode 31
m decreases and becomes 0 at time t5.

By repeating the above operation, FIG.
The horizontal deflection current Idy and the modulation current Im as shown in (k) and (l) can be obtained.

Next, the operation of the entire horizontal deflection circuit will be described with reference to FIG.

FIG. 6A shows the waveform of the horizontal oscillation pulse Vosc. At this time, the voltage Vs input from the terminal 9
w1 (FIG. 6 (c)) is always at the H level, and the transistor 24 is kept conductive. As a result, the voltage Vosc 'becomes almost 0 V (FIG. 6B). Vo
If sc 'is almost always 0 V, the voltage Vrb (FIG. 6)
(F)) has substantially the same waveform as the modulation voltage Vm (FIG. 6 (h)). The resonance capacitor changeover switch 42 includes:
Since a transistor that turns on when the modulation voltage Vm and a specific voltage described later are added is used, only the modulation voltage Vm turns off. As a result, the waveform of the voltage Va1 (FIG. 6 (i)) and the waveform of the collector voltage Vcp of the horizontal output transistor 15 (FIG.
(G)) are substantially equal, and charging and discharging by the resonance capacitor 32 are not performed.

On the other hand, Vsw2 obtained by inverting voltage Vsw1 by transistor 43 (FIG. 6 (d))
Becomes L level. Therefore, power MOSFET 45 is always in a non-conductive state. Thereby, the power MOSFET 45
The waveform of the drain voltage Va2 (FIG. 6 (j)) is substantially the same as the modulation voltage Vm (FIG. 6 (h)), and charging and discharging by the resonance capacitor 33 are not performed.

The operation of the display apparatus when the composite video signal having the higher horizontal frequency is handled has been described above. Next, the operation when the video signal having the lower horizontal frequency is handled will be described.

FIG. 7A shows the waveform of the horizontal oscillation pulse Vosc. FIG. 7B shows a waveform of a pulse Vosc ′ obtained by inverting the horizontal oscillation pulse Vosc by the transistor 23. At this time, the voltage Vsw1 (FIG. 7C) input from the terminal 9 is at the L level, and the transistor 24 is always turned off. As a result, Vosc ′ is supplied to the resonance capacitor switch 42 via the resonance capacitor drive transistor 27 and the resonance capacitor drive transformer 29. At this time, the voltage Vrb (FIG. 7F) is changed to the modulation voltage Vm (FIG. 7).
(H)) and the voltage obtained by inverting the voltage Vosc ′ by the resonance capacitor drive transistor 27 are combined (added). The resonance capacitor changeover switch 42 is turned on while the voltage Vrb is being supplied. That is, the resonance capacitor changeover switch 42 performs horizontal flyback feedback (periods t2 to t4).
, The switching operation to be turned on. Thereby, charge and discharge by the resonance capacitor 32 are performed. At this time, the waveform of the voltage Va1 (FIG. 7)
(I)) has substantially the same waveform as the modulation voltage Vm (FIG. 7 (h)).

On the other hand, Vsw2 obtained by inverting voltage Vsw1 by transistor 43 (FIG. 7 (d))
Becomes H level. Therefore, the power MOSFET 45
Is always in a conductive state, and the drain voltage Va2 (FIG. 7 (j)) of the power MOSFET 45 is always about 0V. Thereby, charging and discharging by the resonance capacitor 35 are performed.

The horizontal deflection current Idy and the modulation current Im when the capacitors 32 and 33 perform charging and discharging are shown in FIG.
(K), the waveform is as shown in FIG.

As described above, the present invention is also applicable to a display device of the type that corrects the pincushion distortion generated in the cathode ray tube.

[0083]

According to the display device of the present invention, since a bipolar transistor having high withstand voltage and low on-resistance can be used as the resonance capacitor changeover switch, a resonance capacitor such as connecting a large-capacity resonance capacitor in series can be used. It is not necessary to take any special measures to gain the combined capacity.

This bipolar transistor is driven with a low loss by a drive transformer. Therefore, the power consumption of the horizontal deflection circuit is reduced.

According to the display device of the present invention, only when the horizontal frequency of the video signal to be handled is low,
It is also possible to set the resonance capacitor changeover switch to perform a switching operation (opening / closing operation in accordance with the horizontal frequency) and to open the resonance capacitor changeover switch when the horizontal frequency of the video signal to be handled is high.

As described above, if the resonance capacitor changeover switch is operated only when the horizontal frequency is low,
As the resonance capacitor changeover switch, an element having a relatively low rating with respect to the operation speed can be used.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of a display device according to the present invention.

FIG. 2 is a circuit diagram of a first embodiment of a display device according to the present invention.

FIG. 3 is an operation waveform diagram (part 1) of the first embodiment of the display device according to the present invention.

FIG. 4 is an operation waveform diagram (part 2) of the first embodiment of the display device according to the present invention.

FIG. 5 is a circuit diagram of a second embodiment of the display device according to the present invention.

FIG. 6 is an operation waveform diagram (part 1) of the second embodiment of the display device according to the present invention.

FIG. 7 is an operation waveform diagram (part 2) of the second embodiment of the display device according to the present invention.

FIG. 8 is a circuit diagram (part 1) showing a part of a conventional display device.

FIG. 9 is a circuit diagram showing part of a conventional display device (part 2).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Horizontal output circuit, 2 ... Horizontal drive circuit, 3 ... Resonant capacitor drive circuit, 4, 42 ... Resonant capacitor changeover switch, 5, 7, 8, 10, 46 ... Power supply voltage input terminal, 6 ... Horizontal oscillation pulse input terminal , 9: resonance capacitor switching signal input terminal, 11: power supply voltage control circuit, 12, 22, 25, 26, 28, 44: resistor,
13: Horizontal drive transformer, 14: Horizontal drive transistor, 15: Horizontal output transistor, 1
6, 30 ... damper diode, 17, 18, 32, 3
3, 34, 35 ... resonance capacitor, 19 ... horizontal deflection coil, 20, 36, 38 ... S-shaped capacitor, 21 ...
Choke coils, 23, 24, 43 ... transistors,
27: resonant capacitor drive transistor, 29
... Resonant capacitor drive transformer, 31 ... Modulation diode, 37 ... Modulation coil, 39 ... Flyback transformer, 40 ... Diode, 41 ... Anode voltage output terminal, 45 ... Power MOSFET, 47 ... Diode
48 horizontal size control circuit 49 horizontal size control signal input terminal 50 signal input terminal 51 signal processing circuit 52 horizontal deflection circuit 53 horizontal oscillation circuit
54 ... video circuit, 55 ... vertical deflection circuit, 56
... deflection yoke, 57 ... cathode ray tube, 60 ... diode

Claims (6)

[Claims] 1. A display device for selectively receiving a plurality of types of video signals having different horizontal frequencies and generating a horizontal deflection current based on the horizontal frequency of the received video signals. A plurality of resonance capacitors connected in parallel; a bipolar transistor connected in series to at least one of the plurality of resonance capacitors to switch an operation state of the connected resonance capacitor; and a horizontal transistor of the received video signal. And a drive transformer for driving the bipolar transistor based on a frequency. 2. The display device according to claim 1, wherein when the horizontal frequency of the received video signal is smaller than a predetermined value, the drive transformer drives the bipolar transistor at the horizontal frequency. Characteristic display device. 3. A display device for detecting a horizontal frequency of an input signal and switching a combined capacitance of resonance capacitors in a horizontal deflection circuit in accordance with the detected horizontal frequency, wherein the horizontal frequency of the input signal is detected. And a switching circuit for switching the combined capacitance, wherein the detection circuit outputs at least two types of detection signals in accordance with the detected horizontal frequency, and the switching circuit comprises: When one of the detection signals is received, the specific resonance capacitor included in the horizontal deflection circuit is charged and discharged in a period of a fixed length, which is repeated at the detected horizontal frequency. When the other of the detection signals of the type is received, charging and discharging by the specific resonance capacitor are suppressed thereafter. Play devices. 4. A detection circuit for detecting a horizontal frequency of an input signal, a horizontal oscillation circuit that oscillates in synchronization with a horizontal frequency of the input signal, and a horizontal drive that operates upon receiving a pulse signal output from the horizontal oscillation circuit. A horizontal output circuit driven by the horizontal drive circuit to generate a horizontal deflection current; a switch circuit connected to a specific resonance capacitor in the horizontal output circuit; and a control circuit controlling the switch circuit. The detection circuit supplies at least two types of detection signals to a control circuit according to the detected horizontal frequency, and the control circuit receives one of the two types of detection signals, and thereafter, the control circuit receives the horizontal signal. Opening and closing the switch circuit in accordance with the pulse signal output from the oscillation circuit and receiving the other of the two types of detection signals, Hereinafter, the display device is characterized in that the switch circuit is opened. 5. The display device according to claim 4, wherein the switch circuit includes a bipolar transistor that opens and closes in accordance with the pulse signal, and wherein the control circuit drives the bipolar transistor. A display device comprising: 6. The display device according to claim 4, wherein a modulation circuit for modulating the horizontal deflection current, and the two kinds of detection signals are selectively received, and the received detection is performed. A circuit for switching an operation state of at least one resonance capacitor included in the modulation circuit according to a signal.