JPH099093A - High voltage generation circuit - Google Patents

Abstract

PURPOSE: To provide a high voltage generating circuit executing the high voltage stabilizing operation and the deflecting operation of high reliability by simplifying circuit configuration. CONSTITUTION: The circuit of a deflection system and the circuit of a high voltage system are constituted by making a horizontal output transistor 6 and a driving power source 16 common. The independent circuit part 20 of the deflection system and the independent circuit part 18 of the high voltage system are respectively connected to the collector side of the horizontal output transistor 6 through diodes 25 and 31 as one-way elements through which currents flow only to the side of the horizontal output transistor 6. The driving power source 16 and the respective independent circuit parts 18 and 20 are connected to each other through choke coils 27 and 24. A pulse width control circuit 19 controls the on-pulse width of the horizontal output transistor 6 corresponding to the dropping quantity of a high output voltage to execute high voltage stabilization. The pulse width control circuit 19 is provided with an on-timing setting means 30, which sets the on starting point of the horizontal output transistor 6 to the first half side compared with the middle point of a scanning period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage generating circuit having a high voltage output voltage stabilizing means.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example of various high voltage generating circuits having a high voltage stabilizing means.

The circuit shown in FIG. 3 (a) is a combination of a deflection system circuit and a high-voltage system circuit. This high-voltage generation circuit has a horizontal output circuit 2 and a flyback transformer 3. Has been done.

The horizontal output circuit 2 comprises a horizontal output transistor 6 as a switch element, a damper diode 7, a resonance capacitor 8, a deflection yoke 10 and an S-shaped correction capacitor 11. The horizontal output transistor 6 receives the voltage pulse sent from the drive circuit (not shown), performs a switching action, and applies a sawtooth current to the horizontal deflection coil of the deflection yoke 10 in cooperation with the damper diode 7. On the other hand, the horizontal output transistor 6
When is off, a flyback pulse is generated by the LC resonance action of the resonance capacitor 8 and the coil component, and this is applied to the flyback transformer 3.

The flyback transformer 3 comprises a core 13 wound with a low voltage coil 14 and a high voltage coil 15. One end of the low voltage coil 14 is connected to the collector side of the horizontal output transistor 6. The end is a high voltage stabilization circuit 12
Is connected to the driving power supply 16 via. The high voltage side of the high voltage coil 15 is connected to the anode of a cathode ray tube (not shown) via a high voltage rectifying diode 17. The flyback transformer 3 boosts the flyback pulse applied from the horizontal output circuit 2 and applies the boosted output (high voltage output voltage) to the anode of the cathode ray tube.

A detection resistor 9 for detecting a high voltage output voltage is connected to the output terminal side of the high voltage coil 15, and the detection voltage of the high voltage output voltage detected by the detection resistor 9 is a high voltage stabilization circuit 12. Has been added to. The high-voltage stabilizing circuit 12 variably adjusts the power supply voltage of the drive power supply 16 in accordance with the amount of drop of the high-voltage output voltage.As the amount of drop of the high-voltage output voltage increases, the power supply voltage of the drive power supply 16 increases. By controlling, the voltage increase of the driving power supply 16 is boosted by the flyback transformer 3 and added to the high voltage output voltage. As a result, the drop amount of the high voltage output voltage is compensated and the high voltage output voltage is stabilized. It

The circuit shown in FIG. 3B is also a circuit in which the deflection system and the high-voltage system are integrated, and the high-voltage stabilizing circuit 12 is provided on the secondary side of the flyback transformer 3. It is a thing. That is, the high-voltage stabilization circuit 12 applies an added voltage to the high-voltage coil 15 according to the amount of drop of the high-voltage output voltage detected by the detection resistor 9 to compensate for the amount of drop of the high-voltage output voltage and stabilize the high-voltage output voltage. Other than that, the circuit operation is the same as that shown in FIG.

FIG. 3 (c) shows a deflection system circuit and a high-voltage system circuit which are formed separately and independently, and each circuit is driven by a separate and independent drive circuit. The circuit on the deflection side has a horizontal output transistor 6a, a damper diode 7a and a resonance capacitor 8a, and the circuit on the high voltage side also has a horizontal output transistor 6b, a damper diode 7b and a resonance capacitor 8b. It has a circuit configuration. A deflection system circuit 5 is a choke coil which functions as a coil element for supplying a current from the driving power supply 16a to the deflection yoke 10. This circuit, like the circuit shown in FIG. 3A, also has a high voltage stabilizing circuit according to the amount of drop in the high voltage output voltage.
The voltage of the driving power supply 16b is varied by 12 to stabilize the high voltage output voltage.

[0009]

However, as shown in FIG. 3 (a), a system in which the deflection system and the high voltage system are integrated and the power supply voltage of the driving power supply 16 is varied to perform the high voltage stabilization control is known. When the power supply voltage of the driving power supply 16 changes, the deflection yoke
There is a problem that the deflection current of 10 changes and the screen of the cathode ray tube is distorted (bent).

Also in the circuit shown in FIG. 3B, when a high-voltage output current flows from the high-voltage coil 15 side to the cathode-ray tube side due to, for example, a change in the brightness of the screen of the cathode-ray tube, the energy of this current is flyback transformer. 3 is generated by being pulled out from the primary side of 3, the deflection current of the deflection yoke 10 changes,
There is a problem that the screen of the cathode ray tube is distorted as the high voltage output current changes.

On the other hand, the circuit of the type in which the deflection system and the high voltage system are separated as shown in FIG. 3 (c) becomes the circuit of the deflection system even if the power supply voltage of the driving power supply 16b is changed by the high voltage stabilizing circuit 12. Is not affected, and problems such as the above-mentioned screen distortion do not occur. However, this separation type circuit requires separate drive circuits for driving the deflection system circuit and the high-voltage system circuit, and the switching operation is performed by the separate horizontal output transistors 6b and 7b. There is a problem that the configuration becomes complicated, the number of parts of the circuit element increases, the device becomes large, and the device cost also increases.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to change the deflection current of the deflection system circuit under the influence of load fluctuations on the high-voltage coil side and high-voltage stabilization control. Another object of the present invention is to provide a high-voltage generation circuit that can simplify the circuit configuration as compared with the conventional independent type of deflection system and high-voltage system.

[0013]

In order to achieve the above object, the present invention is constructed as follows. That is, the high-voltage generation circuit of the present invention has a high-voltage system circuit including a flyback transformer and a deflection-system circuit including a deflection yoke. The high-voltage system circuit and the deflection system circuit include a drive power supply,
The driving power source is independently formed with a switching element that generates a collector pulse in common, and the driving power source is connected to the high voltage system independent circuit section and the deflection system independent circuit section through respective coil elements. The independent circuit section of the system and the independent circuit section of the deflection system are connected to the switch element via a one-way element that passes only the current flowing to the switch element side. A pulse width control circuit is provided for controlling the ON pulse width of the switching element according to the amount of drop in the output voltage to perform stabilization control of the high voltage output voltage, and this pulse width control circuit has an ON start point of the switching element. An on-timing setting means is provided for setting the position on the first half side of the center point of the scanning period.

[0014]

In the present invention having the above-mentioned structure, a collector pulse (flyback pulse) is generated in the high-voltage circuit by the switching action of the common switch element, and the collector pulse is boosted by the flyback transformer to generate a high-voltage output voltage. Added to the cathode ray tube. Further, due to the switching action of the switch element, a deflection current of a sawtooth wave is generated in the circuit of the deflection system, and this deflection current is applied to the deflection yoke to drive the deflection of the beam. When the circuits of the high voltage system and the deflection system are operated, the current of the high voltage system circuit is prevented from flowing to the independent circuit section of the deflection system by the one-way element on the deflection system side. The one-way element on the circuit side of the system prevents it from flowing into the independent circuit part of the high voltage system. This prevents mutual interference between the high voltage system and the deflection system circuits.

Further, in the high-voltage circuit, the pulse width control circuit controls the on-pulse width of the switch element in accordance with the amount of drop of the high-voltage output voltage, and as the amount of drop of the high-voltage output voltage increases, the collector pulse (flyback) is increased. pulse)
Is controlled in such a manner that the peak value of the high voltage is increased, the drop amount of the high voltage output voltage is compensated, and the high voltage is stabilized.

In stabilizing the high voltage, the pulse width control circuit is provided with an on-timing setting means, and the on-start point of the switch element is set to the front half side of the central point of the scanning period. Since the switch element is always turned on while the current flows, the current flowing in the deflection yoke smoothly flows from the negative current of the damper period to the positive current after the end of the damper period, maintaining continuity and stabilizing the high voltage. Even if the on-timing of the switch element is changed according to the on-pulse width by the control of, the deflection current is not affected, and the switching operation of the common switch element affects both the high-voltage system circuit and the deflection system circuit. Suitable circuit operation is performed without affecting each other.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In the following description of the embodiments, the same reference numerals will be given to the same names as in the conventional example, and detailed description thereof will be omitted.

FIG. 1 shows a circuit configuration of an embodiment of a high voltage generating circuit according to the present invention. In this embodiment, one horizontal output transistor 6 functioning as a switching element and one driving power source 16 are shared to form a high voltage system circuit and a deflection system circuit, and a high voltage system independent circuit section 18 and a deflection circuit are provided. The system is characterized in that the independent circuit section 20 of the system is formed separately. The high-voltage independent circuit section 18 includes a damper diode 7a, a resonance capacitor 8a, a flyback transformer 3, and a pulse width control circuit 19 that functions as a high-voltage stabilizing circuit. The coil 14 functions as an inductance element that performs LC resonance with the resonance capacitor 8, and the capacitor 21 is connected in series to the low voltage end (winding end) of this low voltage coil.

Further, a first diode 31 functioning as a one-way element having an opposite polarity when viewed from the horizontal output transistor 6 side is provided between the independent circuit section 18 of the high voltage system and the collector of the horizontal output transistor 6. There is. Also drive power
16 and the high voltage end (winding end) of the low voltage coil 14 of the independent circuit portion 18 are connected via a choke coil 27 as a coil element. Then, the connection portion A between the driving power supply 16 and the choke coil 27, the capacitor 21, the resonance capacitor 8a,
A drive power supply is provided between the common connection portion with the damper diode 7a.
A diode 28 is connected with the 16 side being the cathode side, and a diode 29 is connected between the cathode side of the damper diode 7a and the emitter of the horizontal output transistor 6 with the emitter side being the anode side. These diodes 28 and 29 are provided to pass a damper current.

A horizontal drive signal is applied to the pulse width control circuit 19 from a drive circuit (not shown), and the pulse width control circuit 19 detects the pulse width of this horizontal drive signal by the detection resistor 9. A switch control signal in which the ON pulse width is controlled to increase according to the amount of drop of the high voltage output voltage is applied to the base of the horizontal output transistor 6. In this embodiment, the pulse width control circuit 19 is provided with an on-timing setting means 30. The on-timing setting means 30 indicates the on-start point of the horizontal output transistor 6 as shown in (d) of FIG. , Is set on the first half side of the central point M of the scanning period. As a result, the pulse width control circuit 19
Always applies the rising start point of the on-pulse to the front half side of the center point M of the scanning period, and applies a switch control signal to the horizontal output transistor 6 in which the on-pulse width is widened as the drop amount of the high voltage output voltage increases.

On the other hand, the independent circuit section 20 of the deflection system includes a damper diode 7b, a deflection yoke 10 and an S-shaped correction capacitor.
11 and the resonance capacitor 8b.
The drive power source 16 and the independent circuit 20 are connected via a choke coil 24 that functions as a coil element for flowing the current of the drive power source 16 to the deflection yoke 10, and the damper diode of the independent circuit section 20 of this deflection system. Between the cathode side of 7b and the collector of the horizontal output transistor 6, a second diode 25, which functions as a one-way element having an opposite polarity when viewed from the horizontal output transistor 6 side, is connected. The second diode 25 plays a role of cutting off the current flowing from the high voltage system independent circuit section 18 side to the deflection system independent circuit section 20, and the first diode 31 serves as the deflection system independent circuit section.
It plays a role of interrupting the current flowing from 20 to the independent circuit section 18 of the high voltage system.

The high-voltage system circuit of this embodiment operates in the same manner as the high-voltage system circuit shown in FIG. 3C to generate a collector pulse (flyback pulse) and boost the voltage. On the other hand, the pulse width control circuit 19 of the high voltage system circuit receives the detection voltage of the high voltage output voltage detected by the detection resistor 9 and outputs a switch control signal having a wide ON pulse width according to the amount of drop of the high voltage output voltage. Horizontal output transistor 6
In addition, the peak value of the collector pulse generated on the primary side of the flyback transformer 3 is increased to compensate for the drop in the high voltage output voltage and stabilize the high voltage output voltage. Further, the deflection system circuit also performs the switching operation of the horizontal output transistor 6 in the same manner as the deflection system circuit shown in FIG. 3C, and in cooperation with the damper diode 7b produces a horizontal deflection current of a sawtooth wave, This is added to the deflection yoke 10.

FIG. 2 shows a time chart of the waveform of each circuit portion. 7A shows a collector pulse waveform of the horizontal output transistor 6, FIG. 8B shows a current waveform flowing through the low voltage coil 14 of the flyback transformer 3, and FIG. 7C shows a current flowing through the deflection yoke 10. The horizontal deflection current waveform is shown. Further, (d) of the figure shows a switch control signal waveform outputted from the pulse width control circuit 19, and (e) of the figure shows an independent circuit part of the high voltage system from the drive power source 16 through the choke coil 27. The current waveform flowing through 18 is shown.

As shown in FIG. 2D, when the drop amount of the high voltage output voltage becomes large, the pulse width of the switch control signal becomes wide as shown by the broken line. As the ON pulse width of the switch control signal becomes wider, the current flowing through the choke coil 27 becomes larger and the energy applied to the high-voltage circuit becomes larger, as shown by the broken line in (e) of the figure. The peak value of the collector pulse shown in a) becomes large. That is, as the amount of drop in the high-voltage output voltage increases, the peak value of the collector pulse also increases.Therefore, as the peak value of the collector pulse increases, the added voltage for the increase in the peak value of the high-voltage output voltage also increases. Thus, the drop of the high voltage output voltage is compensated, and the high voltage output voltage is stabilized.

In this embodiment, as described above, the on-timing setting means 30 of the pulse width control circuit 19 sets the start point of the on-rising of the switch control signal to the front half side of the central point M of the scanning period. 2 (c),
As is apparent from (d), the switch control signal is always turned on during the period in which the negative deflection current is flowing, that is, within the damper period, so at the center point M of the scanning period during which the deflection current changes from negative to positive. The deflection current smoothly flows from negative to positive, and even if the ON timing of the horizontal output transistor 6 is variably controlled by the stabilization control of the high voltage output voltage, the deflection current is not affected at all. .

On-timing setting means in this embodiment
As shown in (g) of FIG. 2 without providing 30, when the start point of turning on of the switch control signal is raised in the latter half of the central point M of the scanning period, the switch control is started from the central point M of the scanning period. Since the horizontal output transistor 6 is off in the section of time Δt until the signal starts to turn on, the deflection current cannot flow from the deflection yoke 10 side to the horizontal output transistor 6 side, and the current is 0, At t ₁ when the switch control signal pulse rises and the switch is turned on, the deflection current rises stepwise from 0 to point Q, the deflection current discontinuity occurs in the Δt section, and the screen of the cathode ray tube becomes narrower. Problem arises. In this regard, in the present embodiment, since the ON start rising point of the switch control signal is always on the front half side of the central point M of the scanning period, such a discontinuity of the deflection current does not occur, and As described above, it is possible to perform suitable circuit driving of the deflection system without being affected by the size of the ON pulse width of the switch control signal.

Further, in this embodiment, since the driving power supply 16 and the horizontal output transistor 6 are configured as common circuit elements (circuit parts) of the deflection system circuit and the high voltage system circuit, the conventional example shown in FIG. Compared to the complete separation type circuit of the high voltage system and the deflection system shown in (c), the number of parts of the circuit can be reduced, the circuit configuration can be simplified accordingly, and the cost of the high voltage generation circuit can be greatly reduced.

Moreover, even if the number of parts is reduced, the current flowing in the independent circuit section 20 of the deflection system is blocked by the first diode 31 from flowing to the independent circuit section 18 of the high voltage system.
Similarly, since the second diode 25 prevents the current flowing in the independent circuit unit 18 of the high voltage system from flowing in the independent circuit unit 20 of the deflection system, the circuit operation of the deflection system and the circuit operation of the high voltage system are prevented. Interference is prevented, and stable circuit operation without mutual interference can be performed, similar to the circuit in which the high voltage system and the deflection system shown in FIG. 3C are completely separated.

The present invention is not limited to the above-mentioned embodiment, and various embodiments can be adopted. For example, in the above-described embodiment, the horizontal output transistor 6 is a bipolar transistor as the switch element, but this switch element can be configured by using various other switch elements such as MOS FET (field effect transistor). .

Further, the coil elements for flowing the current of the driving power source 16 to the independent circuit portions 18 and 20 of the high voltage system and the deflection system are formed by the choke coils 27 and 24. This coil element is a pulse transformer other than the choke coil. It is also possible to configure using. By using the choke coils 27 and 24 as pulse transformers, arbitrary outputs can be taken out from the respective pulse transformers. In particular, the output of the pulse transformer instead of the choke coil 27 changes with the high-voltage stabilizing operation, whereas the pulse transformer instead of the choke coil 24 always provides a constant output voltage.

Further, in the above embodiment, the one-way element is constructed by using the diodes 25 and 31, but this one-way element is directed from the independent circuit section 18, 20 side only to the switch element (horizontal output transistor 6) side. Any element may be used as long as it has a function of allowing a current to flow and not allowing a current to flow in the opposite direction, and an element other than a diode may be used.

[0032]

According to the present invention, the switching element for generating the collector pulse and the driving power source are commonly used to perform the circuit operation of the deflection system and the circuit operation of the high voltage system. The number of components of the circuit element can be reduced compared to the case where the deflection system circuit and the high voltage system circuit are operated by using independent switch elements and driving power supplies, respectively, and this simplifies the circuit. Therefore, it is possible to significantly reduce the cost of the high voltage generation circuit.

Further, although the drive power source and the switch element are commonly used, the one-way element is used to prevent mutual interference between the circuit operation of the deflection system and the circuit operation of the high voltage system, and therefore, the circuit of the high voltage system. The problem that the deflection current changes due to the operation does not occur, and it is possible to perform the circuit operation as highly reliable as a circuit in which the deflection system circuit and the high voltage system circuit are completely separated.

Further, according to the present invention, in the high-voltage stabilizing pulse width control circuit provided in the high-voltage circuit, the on-start point of the switch element for generating the collector pulse is located in the front half of the central point of the scanning period. Since the on-timing setting means for setting is provided, the switch element is always turned on within the damper period. Therefore, even if the ON timing of the switch element is variably controlled by the high voltage stabilization control (even if the ON pulse width of the switch element is variably controlled), the current flowing through the deflection yoke of the deflection system circuit is at the midpoint of the scanning period. Therefore, a smooth transition is made from negative to positive without having a discontinuous portion, and it is possible to perform a suitable deflection operation of the deflection system circuit without being affected by the high-voltage stabilization operation. It is possible to sufficiently enhance the reliability of the operation.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a high voltage generating circuit according to the present invention.

FIG. 2 is a time chart showing the operation of each circuit portion of the embodiment.

FIG. 3 is a circuit diagram of various types of conventional high voltage generating circuits.

[Explanation of symbols]

 3 Flyback transformer 6 Horizontal output transistor 10 Deflection yoke 16, 16a, 16b Driving power supply 18 High voltage independent circuit section 19 Pulse width control circuit 20 Deflection independent circuit section 24 Choke coil 25 Second diode 27 Choke coil 30 ON Timing setting means 31 First diode

Claims (1)

[Claims] 1. A high-voltage system circuit having a flyback transformer and a deflection-system circuit having a deflection yoke. The high-voltage system circuit and the deflection system circuit generate a driving power supply and a collector pulse. The driving power source is independently formed in common with the switch element, and the driving power source is connected to the high voltage system independent circuit section and the deflection system independent circuit section through the respective coil elements, and also the high voltage system independent circuit section. The independent circuit part of the deflection system is connected to the switch element via a one-way element that allows only the current flowing to the switch element side to pass through.The high voltage circuit detects the high voltage output voltage and detects the amount of drop in the high voltage output voltage. A pulse width control circuit for controlling the on-pulse width of the switch element to stabilize the high-voltage output voltage is provided according to the above, and this pulse width control circuit starts turning on the switch element. A high-voltage generation circuit provided with an on-timing setting means for setting a point on the front half side of the center point of the scanning period.