JPH0681265B2 - High voltage generation circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-voltage generating circuit provided with a means for stabilizing a high-voltage output voltage applied to an anode of a cathode ray tube.

[Conventional technology]

FIG. 10 shows a conventional high voltage generating circuit. The high voltage generating circuit includes a horizontal deflection output circuit 1 and a flyback transformer 2.

The horizontal deflection output circuit 1 includes a horizontal output transistor 4, a diper diode 5, a resonance capacitor 6, a horizontal deflection coil 7, and an S-shaped correction capacitor 8. The horizontal output transistor 4 receives the voltage pulse sent from the horizontal drive circuit, performs a switching action, and applies a sawtooth current to the horizontal deflection coil 7 in cooperation with the damper diode 5. On the other hand, the resonance capacitor 6 and the horizontal deflection coil 7 generate a flyback pulse due to its resonance action, and the flyback pulse is generated by the flyback transformer 2.
Add to.

The flyback transformer 2 consists of a low voltage coil 11 and a high voltage coil 12 wound around a core 10. One end of the low voltage coil 11 is connected to the collector side of the horizontal output transistor 4, and the other end of the coil 11 is an input. Connected to power supply 13.
The high voltage side of the high voltage coil 12 is the high voltage rectifier diode 14
Is connected to the anode 16 of the cathode ray tube 15 via the, and the other end of the coil 12 is connected to the ABL (Automatic Brightness Limiter) side. The flyback transformer 2 boosts the flyback pulse applied from the horizontal deflection output circuit 1 and applies the boosted output (high voltage output voltage) to the anode 16 of the cathode ray tube 15.

Generally, the high-voltage coil 12 is wound in multiple layers via a diode 17 as shown in FIGS. 10 to 12, and the coils between the layers are wound with the same number of turns, the same winding width, and the same winding pitch, and
The winding end of each layer and the winding start of the next layer
If the polarities are the same at 17, the potential difference between the coils of each layer becomes zero in terms of alternating current. Therefore, the insulation treatment between the respective layers only needs to consider the potential difference of the direct current, and it is not necessary to consider the heat generation due to the dielectric loss, so that the insulation treatment becomes easy.

Further, if the high voltage coil 12 is wound in multiple layers as described above,
Since the insulation distance between the low-voltage coil 11 and the high-voltage coil 12 can be made smaller than that of other section winding coils, the finished outer diameter of the coil outermost layer can also be made small. As a result,
As shown in FIG. 13, there is an advantage that the leakage inductance of the high voltage coil 12 can be reduced, and for this reason, the flyback transformer 2 in which the coil 12 is a multi-layer winding type is widely used.

However, as shown in FIG. 13, the high voltage output current I _H flowing from the coil 12 to the anode 16 of the cathode ray tube 15 is 0 to 200 μ if the high voltage coil 12 is wound in multiple layers (multilayer winding).
It fluctuates rapidly in the range of A, and an unfavorable phenomenon occurs.
Therefore, in recent years, as shown in FIG. 10, a fixed resistor 18 and a variable resistor 20 are arranged in series between the high-voltage output side (the anode side of the cathode ray tube 15) and the ground, and the high-voltage output current is increased.
About 10% of I _H is shunted to prevent a sudden change in the high voltage output current, as shown in FIG.

That is, in the characteristic diagrams shown in FIGS. 13 and 14,
If a variable setting range of the high voltage output current I _H is set to a range of 0～1000Myuei, if not taken shunt means of the high-voltage output current I _H, the output impedance Z ₀₁ and Z from FIG. 13 ₀₁
= (27-25) KV / 1000 μA = 2 MΩ. On the other hand, I
If you take measures to divide _H , output impedance Z ₀₂ will be 14th.
From the figure, Z ₀₂ = (26.1−24.9) KV / 1000μA = 1.2MΩ, which means that the output impedance was considerably improved.

[Problems to be Solved by the Invention]

However, today, the demand for higher definition in the image quality of the cathode ray tube 15 is becoming stronger and stronger, and it is desired to further reduce the output impedance. Moreover, when lowering the output impedance, a means without power loss is strongly desired, and as described above, a method for shunting I _H via the fixed resistor 18 and the variable resistor 20 is:
It is no longer possible to meet such demand, and it is no longer accepted by the market.

The present invention has been made in view of the above circumstances, and an object thereof is to significantly reduce the output impedance without causing power loss, in other words, to stabilize the high voltage with respect to changes in the high voltage output current. It is to provide a high-pressure generator capable of performing.

[Means for Solving the Problems]

In order to achieve the above object, the present invention is configured as follows. That is, according to the present invention, a flyback pulse applied from a horizontal deflection output circuit is boosted by a flyback transformer, and a high voltage output voltage is applied to a cathode of a cathode ray tube from a high voltage side of a high voltage coil constituting the transformer. The addition voltage generating coil wound around the core of the back transformer and generating the addition voltage, and the addition voltage generated by the addition voltage generating coil are controlled, and a correction voltage that increases as the drop amount of the high-voltage output voltage increases A multiplying voltage circuit configured to have an addition voltage control circuit for outputting and a plurality of capacitors and diodes to boost the correction voltage from the addition voltage control circuit and apply the boosted output to the cathode of the cathode ray tube via a high voltage coil. Then, while the high voltage output current is flowing from the high voltage coil to the cathode of the cathode ray tube, the high voltage suddenly increases. It is configured as a; and a discharge circuit for discharging electric charge of the capacitor that remain charged among capacitors of the multi-precision pressure circuit when the output current has sharply to almost zero.

[Action]

In the present invention configured as described above, when a high voltage output current flows to the anode of the cathode ray tube due to brightness increase adjustment or the like, the high voltage output voltage decreases. The addition voltage control circuit controls the addition voltage generated in the addition voltage generation coil based on the drop amount of the high voltage output voltage, and if the correction voltage corresponding to the drop amount of the high voltage output voltage, that is, the voltage drop amount becomes large. A large correction voltage is applied to the multiple voltage circuit accordingly. The multiple voltage circuit boosts this correction voltage and applies it to the high voltage coil. As a result, the drop in the high voltage output voltage is supplemented and the high voltage output voltage is stabilized.

Also, when the screen of the cathode ray tube suddenly goes dark (when the high-voltage output current is maximally flowing) from the maximum bright state (when the high-voltage output current becomes zero) during circuit operation, multiple pressure Even if some of the plurality of capacitors included in the circuit are still charged, the charges of the capacitors are quickly discharged by the discharge circuit. Therefore, a high voltage higher than the reverse withstand voltage is not applied to a circuit element such as a transistor forming the added voltage control circuit from the capacitor side, and the circuit element can be protected.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same circuit parts as those in the conventional example are designated by the same reference numerals, and the duplicated description will be omitted.

FIG. 1 shows a circuit configuration showing an embodiment of the present invention.

This embodiment is different from the conventional example in that the reference voltage generation circuit 3, the voltage detection unit 9, and the addition voltage generation coil 21
That is, the comparison amplifier 22, the switching circuit 23, the switching operation control circuit 39, the multiple voltage circuit 46, and the discharge circuit 60 are provided. Of these, the reference voltage generation circuit 3, the voltage detection unit 9, the added voltage generation coil 21,
The combination of the comparison amplifier 22, the switching circuit 23, and the switching operation control circuit 39 constitutes an addition voltage control circuit.

The added voltage generating coil 21 is a flyback transformer 2
Is wound around the core 10 while being insulated from other coils, and an input tap 19 is provided on the winding start end side of the coil 21, and an output end side (winding end side) of the coil 21. ) Is provided with an output tap 24. This output tap 24
Outputs the added voltage generated in the coil 21.

On the other hand, one end of a fixed resistor 28 is connected to the high voltage side of the high voltage coil 12 (cathode side of the high voltage rectifier diode 14), and the other end of the fixed resistor 28 is a variable resistor for focus output adjustment.
VR _F , variable resistor VR _S for screen voltage adjustment, variable resistor VR ₁ for high voltage output voltage adjustment are connected in series in sequence,
Among them, the fixed resistor 28 and the variable resistors VR _F and VR _S are the circuit parts of the focus pack, and the variable resistor VR ₁ constitutes the voltage detection unit 9 of the high voltage output voltage E _H. There is. The other end of the variable resistor VR ₁ is connected to the reference potential (ground side in the figure).

The variable resistor VR ₁ has a high voltage output voltage E
_H is detected, and the detected voltage e ₆ is applied to the plus side input terminal of the comparison amplifier 22.

The reference voltage generation circuit 3 includes a control voltage generation coil 25, a rectifier 26, a rectangular wave output circuit 27, a fixed resistor 29, and an integration circuit 31, and the rectangular wave output circuit 27 includes an amplifier 32 and a clip circuit. It consists of 33.

The control voltage generating coil 25 is the core of the flyback transformer 2.
The coil 10 is insulated from other coils and wound around the low voltage side to generate a control voltage e ₂ having a flyback pulse waveform shown in FIG. 2 (a). The high voltage side (winding end side) of the control voltage generating coil 25 is connected to a reference potential (earth side in the figure), and the low voltage side (winding start side) of the coil 25 is a fixed resistor 29.
Is connected to the negative terminal of the amplifier 32 via.
The positive side terminal of the amplifier 32 is connected to the reference potential (ground side in the figure), and between the positive side terminal and the negative side terminal of the amplifier 32, the negative side terminal is the cathode side and the rectifier ( In the figure, a diode) 26 is connected. When the input of the amplifier 32 is formed by the base of a transistor, the input waveform is rectified by the equivalent diode between the base and the emitter of the transistor, so that the rectifier 26 is unnecessary.

The rectifier 26 controls the voltage e ₂ generated by the control voltage generating coil 25.
Is rectified (the negative component is cut) and only the positive component of the voltage e ₂ is input to the inverting input terminal of the amplifier 32, that is, the negative side terminal. Amplifier 32 amplifies this input voltage and applies its output to clip circuit 33. The clip circuit 33 cuts off the head of the voltage waveform amplified by the amplifier 32,
As shown in FIG. 2B, a rectangular wave having a pulse width in the blanking period Tr (in the present specification, the rectangular wave is used in a broad sense including not only a rectangular waveform but also a square waveform). ) Voltage e ₃ is generated and is added to the integrating circuit 31. This integrator circuit 31 integrates the rectangular wave voltage e ₃ over the period of the blanking period Tr, sets the position of the starting point of the blanking period to zero, as shown in FIG. Creates a rising waveform with a peak value at the position. In this case, the return period
Since the integration is not performed in the range that exceeds Tr, the voltage waveform drops to the right due to discharge from the peak position (discharge from the capacitor of the integration circuit), etc., and overall it peaks at the end position of the blanking period Tr. Triangular wave (sawtooth wave) voltage e ₅
Is created. This triangular voltage waveform maintains a constant shape in any blanking period Tr. This triangular wave voltage e ₅
Is applied to the negative input terminal of the comparison amplifier 22.

The comparison amplifier 22 compares the triangular wave voltage e ₅ with the detection voltage e ₆ applied from the variable resistor V _R1 of the voltage detection unit 9 (second
(C)), section where triangular wave voltage e ₅ exceeds detection voltage e ₆ △
t only becomes a constant voltage of negative (including zero) (t ₃ period interval and t ₇ ~t ₁₀ of ~t ₅ in the figure), otherwise control a positive certain level of voltage, including a scanning period Inverting amplifier for signal e ₇
Add to 54. Then, the output signal e ₈ whose polarity is inverted by the inverting amplifier 54 is added to the switching circuit 23. In the present specification, the comparison amplifier 22 compares the triangular wave voltage e ₅ with the detection voltage e ₆ and outputs a voltage corresponding to the difference, so long as it is a circuit regardless of the name. Any circuit may be used, and for example, it is used to include various circuits equivalent to these, such as a differential amplifier, a comparator, an operational amplifier, and the like.

The switching circuit 23 includes a drive transistor 34, diodes 35 and 36, resistors 37 and 38, a capacitor 40, a drive power supply 41, a drive transformer 42, and a control transistor.
It consists of 43 and. In the drive transistor 34, the base side is connected to the output terminal of the inverting amplifier 54, and the emitter side is connected to the common connection portion between one end side of the resistor 37 and the capacitor 40 and the negative side of the driving power supply 41. The common connection is further connected to a reference potential (ground side in the figure).
The other ends of the resistor 37 and the capacitor 40 are commonly connected to the cathode side of the diode 35,
The anode side of is connected in common to the connection portion between the collector of the drive transistor 34 and the high voltage side (winding end side) of the primary coil 44 forming the drive transformer 42. These resistor 37, capacitor 40, and diode 35 form a snubber circuit. Further, the low-voltage side (winding start side) of the primary coil 44 is connected to the positive side of the drive power supply 41 via the resistor 38.

On the other hand, in the secondary coil 45 of the drive transformer 42, the low voltage side (winding start side) is connected to the base side of the control transistor 43, and the high voltage side (winding end side) of the coil 45 is the emitter side of the control transistor 43. And the diode 36 on the anode side are commonly connected, and this common connection serves as the output terminal of the switching circuit 23 and is connected to the input terminal of the multiple voltage circuit 46. The collector side of the control transistor 43 is connected to the cathode side of the diode 36.
The connections of 3, 36 are connected to the output tap 24 of the added voltage generating coil 21. The low voltage side (winding start side) of the added voltage generating coil 21 communicates with the ABL side via the input tap 19.

The diode 36 is for flowing a reverse current from the emitter side to the collector side of the control transistor 43, and therefore the control transistor 43 is formed of a transistor such as a bipolar transistor in which a reverse leakage current flows. Sometimes diode 36 is not necessary and can be omitted. This switching circuit 23
When the control signal e ₇ has a voltage of zero, in other words, when the output signal e ₈ from the inverting amplifier 54 has a positive voltage, the gate is opened for a predetermined period to be described later and the pulse voltage shown in FIG. e ₁₂ is added to the multiple voltage circuit 46.

A switching operation control circuit 39 is connected to the input end side of the switching circuit 23. The switching operation control circuit 39 includes a first transistor 47 and a second transistor 47.
It consists of 48 and a differentiating circuit 50. Both transistors 47,4
The collectors of 8 are commonly connected to the base side of the drive transistor 34, and the emitters of both transistors 47 and 48 are commonly connected to the emitter side of the drive transistor 34. The base of the first transistor 47 is connected to the output terminal side of the fixed resistor 29, and
The base of the second transistor 48 is connected to the output terminal of the clipping circuit 33 via the differentiating circuit 50.

The multiple voltage circuit 46 includes first to third diodes 51, 52,
53 and first to third capacitors 55, 56, 57. The anode side of the first diode 51 is connected to the emitter side of the control transistor 43, and the cathode side of the diode 51 is the second diode 52.
On the anode side of the diode 52, the cathode side of the diode 52 is connected to the anode side of the third diode 53 to form a diode series connection body. The cathode side of the third diode 53 is connected to the high voltage coil 12 of the high voltage coil 12. It is connected to the low voltage side.

Further, one end of the first capacitor 55 is connected to a common connection portion between the emitter of the control transistor 43 and the anode of the first diode 51, and the other end of the capacitor 55 is the cathode of the second diode 52. Side and the anode side of the third diode 53 are connected to each other. And the second
One end of the capacitor 56 is connected to the connection between the cathode of the first diode 51 and the anode of the second diode 52, and the one end of the third capacitor 57 is connected to the cathode of the third diode 53. These are connected to the side
The other ends of the second capacitor 56 and the third capacitor 57 are both connected to the ABL side. The anode side of the diode 58 is connected to the ABL side, and the cathode side of the diode 58 is connected to the first diode 51 and the second diode 52 or the second diode 52 and the third diode 53.
And a connection portion (a connection portion between the first diode 51 and the second diode 52 in FIG. 1).

The discharging circuit 60 is composed of a resistor 61 and a diode 62. One end of the resistor 61 is connected to the low voltage end of the added voltage generating coil 21, and the other end is connected to the anode of the diode 62. The cathode of the diode 62 is connected to the emitter side of the control transistor 43, that is, the input end side of the multiple voltage multiplying circuit 46.

The present embodiment is configured as described above, and the stabilizing action of the high voltage output voltage E _H will be described below.

When the brightness of the cathode ray tube 15 is increased, the high voltage output current I _H flows through the anode 16, and the high voltage output voltage E _H drops due to the internal impedance of the high voltage generator, etc.
The voltage e ₆ detected at will also decrease. As shown in FIG. 2C, when the detection voltage e ₆ drops, the detection voltage e ₆ drops below the peak position of the triangular wave voltage e ₅ produced by the integrating circuit 31, so that Δ in the blanking period The triangular wave voltage e ₅ exceeds the detection voltage e ₆ in the interval t _{1 and} the interval Δt ₂ that exceeds the blanking period. FIG. 2 (c) shows a case where the detection voltage e ₆ detected in the period of t _{7 to} t _{10 is} lower than the detection voltage e ₆ detected in the period of t _{3 to} t _5. As the detection voltage e ₆ , that is, the high-voltage output voltage E _H decreases, Δt (however,
Δt = Δt ₁ + Δt ₂ ) becomes wider and the negative voltage (zero voltage in the figure) of the control signal e ₇ output from the comparison amplifier 22 becomes wider (FIG. 2 (d)). ). The waveform of the control signal e ₇ is inverted by the inverting amplifier 54, and its output voltage e ₈ is applied to the switching circuit 23. (In this case, when the waveform of e ₇ is inverted by the inverting amplifier 54, the waveform of e ′ ₈ (FIG. 2 (e)) is obtained, but the scanning period T _S is the period of t _{4 to} t ₅ and t _{9 to} t _10. As described later, since the control transistor 43 is cut off as described later, it is equivalent to the voltage of the waveform of e ₈ being applied to the base of the drive transistor 34.) e ₈ is a switching circuit
The circuit operation when added to 23 is as follows.

First, when the detected voltage e ₆ is between the voltage at the starting point (zero voltage) of the triangular wave voltage e ₅ and the peak value voltage, during the retrace period Tr from t ₁ to t ₃ , the triangular wave voltage e 6 _{Since the} detection voltage e ₆ is larger than ₅ , the inverting amplifier 54
Apply e ₈ to the base of drive transistor 34. As a result, the drive transistor 34 is cut off, and the collector voltage e ₁₀ (FIG. 2 (j)) of the transistor 34 becomes a positive voltage. As a result, current does not flow from the drive power source 41 to the primary coil 44 of the drive transformer 42, and the transformer 42 is turned off. As a result, the base voltage e ₁₁ (FIG. 2 (k)) of the control transistor 43 becomes zero. Therefore, the control transistor 43 is cut off to close the gate. Therefore, the added voltage is generated from the added voltage generation coil 21 to the multiple voltage circuit 46.
e ₁₂ (Fig. 2 (m)) is not added.

Next, in the t ₃ ~t ₄ sections retrace period Tr, an rise in because smaller for the detection voltage e ₆ than the triangular wave voltage e _5, the control signal e ₇ rises downwardly t ₃ (herein The term ‘0’ is used not only when it rises upward but also when it rises (falls) downward, and accordingly, the inverting amplifier 54 applies a positive voltage e ₈ to the base of the drive transistor 34. As a result, the same transistor 34
Turns on, and a current flows from the drive power supply 41 to the primary coil 44. And control transistor through the secondary coil 45
A positive pulse e ₁₁ is applied to the base of 43, turning on the transistor 43. At this time, the added voltage generating coil
A flyback pulse e ₁ of about 1000 V (FIG. 2 (L)) is generated at the output end of 21, and this added voltage e ₁ is applied from the output tap 24 to the collector of the control transistor 43.

Therefore, since the transistor 43 is turned on and the gate is opened in the section of t _{3 to} t ₄ (section of Δt ₁ ), the peak value voltage e ₁₂ of the waveform part of the section of e ₁ (Fig. 2 (m) ) Passes through the gate of the transistor 43 from the emitter side to the multiple voltage circuit 46
Added to.

Next, t the t ₃ as in the case of ~t ₄ sections holds the relationship of e _5> e ₆ in ₄ ~t ₅ sections, although positive pulse e ₁₁ is applied to the base of the control transistor 43 Since the period from t _{4 to} t ₅ is in the scanning period, the negative voltage component E _N of the added voltage e ₁ is applied to the collector side of the transistor 43, and the transistor 43 is turned off to close the gate. Therefore, the voltage e ₁₂ applied from the emitter side of the transistor 43 to the multiple voltage circuit 46 becomes zero.

Next, in the section from t _{5 to} t ₆ , the relationship of e ₆ > e ₅ is established, the drive transistor 34 and the control transistor 43 are cut off, and the transistor 43 closes the gate, so that the voltage applied to the multiple voltage circuit 46 is increased. e ₁₂ becomes zero.

As described above, when the detection voltage e ₆ is between the voltage of zero voltage and a peak value of the triangular wave voltage e _5, the switching circuit 23 the control signal e ₇ within blanking period becomes the voltage of the zero position open the gate only from (positive voltage from a position which rises in the negative direction to the zero voltage) to the position of the end point of the flyback period △ t ₁ interval, the voltage e ₁₂ waveform portion of the section of the addition voltage e ₁ Is added to the multiple voltage circuit 46. In this case, the lower the high-voltage output voltage E _H , the larger the width of Δt _{1 and} the longer the gate opening time.
The voltage e ₁₂ applied to the multiple voltage circuit 46 from 23 also increases.

Next, when the detection voltage e ₆ is equal to or larger than the peak value of the triangular wave voltage e ₅ , that is, when there is no voltage drop in the high-voltage output voltage E _H , the triangular wave of e ₅ and e ₆ cross each other. Therefore, the pulse of the control signal e ₇ is not generated and the signal e ₇
Is a positive constant level voltage from the blanking period Tr to the scanning period T _H.

As a result, the output voltage e ₈ from the inverting amplifier 54 becomes zero,
The drive transistor 34 and the control transistor 43 are not cut off and the voltage e ₁₂ is not applied to the multiple voltage circuit 46.

Then, when the detection voltage e ₆ becomes lower than the voltage (zero voltage) of the starting position of the triangular of the triangular wave voltage e _5, since e ₇ becomes zero voltage over the entire period of the scanning period and the blanking period, e ₈ becomes a positive voltage (positive DC voltage), which causes a disadvantage that the voltage e ₁₂ is not applied to the multiple voltage circuit 46, although the high-voltage output voltage E _H drops significantly.

In the present embodiment, such an inconvenience is solved by providing the first transistor 47 as follows. FIG. 3 shows the waveform of each circuit portion when the first transistor 47 is provided under the condition of e ₆ <0. This e ₆ <
Under zero, the pulse e ₉ (the voltage on the base side of the first transistor 47 from the output terminal side of the fixed resistor 29 is positive during the scanning period and zero during the blanking period (see FIG. 2 (i. )) Is being applied. Therefore, the first transistor 47 is cut off in the blanking period Tr, and the collector voltage of the first transistor 47 becomes a positive voltage. That is, the pulse e _{8 that} is positive in the blanking period Tr is applied to the base of the drive transistor 34, and as a result, the drive transistor 34 is turned on and the gate is opened during the entire blanking period. On the other hand, at this time, a pulse current I ₂ (FIG. 3 (c)) starting from the starting point of the blanking period flows through the base of the control transistor 43. Along with this, the pulse current I is applied to the collector side of the control transistor 43 in a section that is almost the same as the pulse section of I _2.
1 (Fig. 3 (d)) flows. As a result, the component of the added voltage e ₁ corresponding to the pulse width of I ₁ (the shaded portion of the waveform in FIG. 3 (e)) is applied to the high voltage coil 12 via the multiple voltage circuit 46.

However, when the switching circuit 23 is configured using the general drive transformer 42, the end point position of the pulse of I ₁ is sufficiently before the peak position of the pulse of e ₁ (ON period of the control transistor 43). Is too short),
The disadvantage that the voltage e ₁₂ applied to the high voltage coil 12 cannot be increased occurs. Of course, if the number of coil turns of the drive transformer 42 is increased or the core is increased,
The pulse width of I ₁ can be increased and the applied voltage e ₁₂ can be increased, but this increases the capacity of the drive transformer 42 and lengthens the operating time, which causes heat generation and consumption by the drive transformer 42 and the control transistor 43. There arises a new problem that the electric power becomes large and the drive transformer 42 also becomes expensive.

In this embodiment, in order to effectively solve such a problem,
A differentiating circuit 50 and a second capacitor 56 are provided.

FIG. 4 shows the waveform of each circuit portion under the condition of e ₆ <0 when the differentiating circuit 50 and the second capacitor 56 are provided. Under this condition of e ₆ <0, the differentiating circuit 50 differentiates the output voltage e ₃ from the clipping circuit 33, and the fourth
The differential output e ₁₃ shown in FIG. 6F is applied to the base of the second transistor 48.

The second transistor 48 has an operating voltage E ₁₃ with a differential output e ₁₃ ,
In other words, it turns on in the interval of Δt ₁₃ from the start position of the blanking period Tr. Since the drive transistor 34 is cut off in the interval Δt ₁₃ in which the second transistor 48 is on, the control transistor 43 is also off. On the other hand, △ t ₁₃
After the period of, the voltage of e ₁₃ becomes lower than that of E ₁₃ ,
The second transistor 48 is cut off, the drive transformer 42 is turned on accordingly, the pulse current I ₂ (FIG. 4 (c)) flows to the base of the control transistor 43, and the transistor 43 receives the pulse current on the collector side. I ₁ (Fig. 4 (d))
Turn on only in the section where is flowing. As a result, the voltage e _{12 in the} shaded area of the added voltage e ₁ (FIG. 4 (e)) corresponding to the pulse section of I ₁ is applied to the multiple voltage circuit 46.
Thus, the differential output e ₁₃ causes the control transistor 43
The ON position of is shifted, and the control transistor 43 is turned on with the peak of the waveform of I ₁ and the peak of the waveform of e ₁ being matched.
Even when 42 is used, a large added voltage e ₁₂ can be applied to the high voltage coil via the multiple voltage circuit, and the problems such as heat generation due to the size increase of the drive transformer 42 can be effectively eliminated. You can

The multiple voltage circuit 46 is the voltage applied from the switching circuit 23.
e ₁₂ is boosted as follows and added to the high voltage coil 12 of the flyback transformer 2. This step-up operation will be described with reference to equivalent FIG. 5 to FIG. 7 extracted from the circuit of FIG. 1. First, in the blanking period Tr, the current is drawn by the route of a of FIG. Flows and the second capacitor 56 is charged with the voltage of E ₁₂ (E ₁₂ is the peak voltage value of the voltage e ₁₂ ). Next, in the scanning period, a current flows through the route of b shown in FIG. 6, and the voltage of E ₁₂ + E ₁₂ is charged in the first capacitor 55. Next, in the retrace line period again, c in FIG.
A current flows through the route of, and the third capacitor 57 is charged with a voltage corresponding to the added voltage of the voltage of E _{12 and} the voltage of the first capacitor 55. By repeating such a boosting operation, the voltage of 2 (E ₁₂ + E _N ) is finally charged in the third capacitor 57, and this voltage is applied to the high voltage coil 12. This voltage of E _{N is} the voltage of the negative component of the waveform of the added voltage e ₁ . That is, in the circuit of FIG. 1, but multiple precision pressure circuit 46 functions as a triple pressure circuit if you include a function to have (alternating current component as a double pressure circuit, since E _N is sufficiently small compared to the E ₁₂ You can ignore it and think of it as a double voltage circuit in the flyback transformer circuit.

When the control transistor 43 is cut off, the high voltage current I _H flows through the route shown in FIG.

Generally, in this type of circuit, it may be necessary to flow a high voltage output current even when the high voltage output voltage E _H exceeds the correction range during circuit operation.In this embodiment, the anode is connected to the ABL side. By arranging a diode 58 having a cathode connected to the connection portion of the cathode of the first diode 51 and the anode of the second diode 52, the object is achieved.

By the way, in general, when the screen of the CRT 15 suddenly changes from a bright state to a dark state, in other words,
When the high voltage output current suddenly changes from the maximum value to zero, the control transistor 43 is cut off. At the time of this cutoff, the second capacitor in the multiple voltage circuit 46
The electric charge charged in 56 and the third capacitor 57 is immediately discharged through the high voltage coil 12, but the first capacitor 55 is positive in the right side of the plate in FIG. Since the left side is the negative side and the electric charge is charged,
There is an inconvenience that the discharge route of the charge is closed.

When the discharge route is closed in this way, the first capacitor 55 remains at the maximum charging voltage, so the control transistor 43 receives the sum of the maximum charging voltage of the capacitor 55 and the added voltage e _1. As a result, the reverse breakdown voltage of the control transistor 43 becomes a problem (a voltage higher than the reverse breakdown voltage is applied to the control transistor 43, which causes a problem of destruction of the transistor 43).

In this embodiment, a discharge circuit is provided from the viewpoint of preventing such a problem.
60 are provided. That is, by providing this discharge circuit 60, as shown in FIG.
At the time of cutoff of 43, the electric charge charged in the first capacitor 55 is promptly discharged in the path that passes through the resistor 61, the diode 62, the first capacitor 55, and the third diode 53 in this order. The problem of reverse breakdown voltage of the control transistor 43 is solved.

By the way, the current i flows through the discharge circuit 60 during both the blanking period and the scanning period, and there is some concern about power loss in the resistor 61 due to the current flow.

However, during the blanking period, the resistance value of the resistor 61 is changed to 50K.
When the control transistor 43 is cut off, the load impedance at the output end of the multiple voltage circuit 46 becomes several 100 MΩ, and the resistance value of the resistor 61 is sufficiently smaller than the load impedance. The power consumption due to is almost negligible.

On the other hand, during the scanning period, the current i
However, at this time, when the voltage between the peaks of the added voltage e ₁ generated by the added voltage generation coil 21 (the voltage between the peak on the peak side and the peak on the valley side of the voltage pulse waveform) is about 1000V, normally e ₁ Voltage of negative component of (voltage across resistor 61)
E _N is about 100V, and when the resistance value of resistor 61 is 50kΩ,
The power loss in the resistor 61 is as small as 0.2W at most,
This is also a value that can be ignored. Therefore, the power loss in the resistor 61 is practically not a problem.

As described above, according to the present embodiment, the time Δt ₁ for opening the gate of the switching circuit 23 is controlled corresponding to the drop amount of the high-voltage output voltage E _H , so if the drop amount of E _H is large. The time it takes to open the gate will be longer, so E _H
The voltage e ₁₂ added to the signal also increases, and the circuit operates in the direction of keeping E _H constant. In the operation of stabilizing the high voltage output voltage E _H , when the detection voltage e ₆ is lower than the starting point position of the triangular wave of the reference voltage e ₅ , that is, when e ₆ <0, the differentiating circuit 50 and the second transistor In cooperation with 48, the ON operation position of the control transistor 43 is shifted by Δt ₁₃ from the starting point position of the blanking period, and the peak of the waveform of e ₁ and the peak of the waveform of the current I ₁ on the collector side coincide with each other. Since the gate of the control transistor 43 is controlled to open by the short pulse width of I _1, the large voltage e ₁₂ passes through the voltage multiplier circuit 46 despite the short ON time of the control transistor 43. As a result, the high voltage output voltage E _H is effectively prevented from being suddenly decreased. Further, in this case, the control transistor 43 is not turned on during the entire blanking period Tr, but is turned off while the second transistor 48 is turned on. The interval in which the limit on operation is possible is limited to Δt ₃ in FIG. By limiting the ON period of the control transistor 43 as described above, heat generation from the transistor 43 and the drive transformer 42 can be reduced, and power consumption can be reduced.
The drive transformer 42 having a small capacity can sufficiently achieve the purpose of stabilizing E _H.

Further, the switching operation of the switching circuit 23 is performed by the on / off operation of the control transistor 43, but the off operation is automatically turned off by entering the scanning period even if the operating voltage e ₁₁ is applied to the base side. Since the operation is performed, the fall performance of the transistor 43 is irrelevant as far as the switching off action is concerned. Therefore, as the performance of the transistor 43, it is sufficient to consider only the rising performance of the ON operation, and good switching operation can be performed even if a transistor having a poor falling performance is used. Further, the voltage e applied to the control transistor 43
_{Since 11} is stepped down by the drive transformer 42 and added, the control transistor 43 does not have to have a high withstand voltage, and a product with a withstand voltage of about 1500 V can achieve the purpose sufficiently according to the so-called V _CBO standard. The cost of the transistor 43 used and the size of the transistor can be reduced. In addition, as in the present embodiment, the drive transformer 42
By providing the above, it is possible to reduce the power loss of the drive transistor 34.

Further, since the high-voltage output voltage is controlled on the high-voltage side (secondary side) of the flyback transformer, it does not adversely affect the voltage fluctuation of the deflection coil and the like, and therefore the screen does not deteriorate.

Further, in this embodiment, the pulse width can be controlled within the blanking period with a small circuit configuration, and moreover, since this pulse width control is performed within the blanking period, the switching noise of the switching circuit may appear on the screen. In addition, the heat generation of the transistor used for switch control can be reduced.

Further, in this embodiment, the added voltage generating coil and the control voltage generating coil used in the reference voltage generating circuit can be wound around the core of the flyback transformer. It becomes easy to insulate the hot side and the cold side in alternating current.

Further, since the ground of the switching circuit of this embodiment does not necessarily have to be the line on the ABL side, the degree of freedom in circuit design can be increased.

The present invention is not limited to the above embodiments, and various modes of implementation can be adopted. For example, in the circuit shown in FIG. 1, the fixed resistors 28, 29, 38 and the snubber circuit in the switching circuit 23 may be omitted if necessary.

Further, in the present embodiment, the double voltage circuit is used as the multiple voltage circuit 46, but it may be constituted by a circuit of different double voltage such as triple pressure, quadruple pressure, or the like.

Further, in the above embodiment, the added voltage control circuit is composed of the circuit of the pulse width control system, but unlike this, it may be composed of the circuit of another system.

Further, in the circuit of FIG. 1, the high-voltage coil 12 may be a multi-layer laminated winding, in which case, as shown in FIG. 10, the diode 17 is provided between the coils of each layer.

Further, in the above embodiment, the voltage detection unit 9 directly takes out the high voltage output voltage E _H to obtain the detection voltage e ₆ , but it is also possible to take out the high voltage output voltage and indirectly obtain the detection voltage e _6. Good. In this case, the extracted high-voltage output current is AB
Since it is introduced from the L side to the comparison amplifier 22 via a resistor, some circuit changes are required.

Further, in the above embodiment, the discharge circuit 60 is composed of the resistor 61 and the diode 62, but other circuits, for example, a normal thermistor or a positive temperature coefficient thermistor having general characteristics, or a circuit element such as a Zener diode is used. You may comprise.

〔The invention's effect〕

The invention as described above, when the high output voltage E _H by flowing high voltage output current I _H drops controls the addition voltage, the correction voltage corresponding to the drop of the high voltage output voltage E _H multi Since the voltage is applied to the high-voltage coil via the voltage doubler circuit, the voltage corresponding to the voltage drop is replenished to the high-voltage coil, which stabilizes the high-voltage output voltage and effectively distorts the screen. Can be prevented. This leads to an extremely small output impedance of the high-voltage generating circuit, which makes it possible to sufficiently meet the demand for higher definition of image quality. Further, since the correction voltage output from the added voltage control circuit is boosted by the multiple voltage circuit and applied to the high voltage coil, for example, the multiple of the multiple voltage circuit is set to N times, and the drop amount of the high voltage output voltage is increased. If the voltage required for compensation is E _V , the correction voltage output from the addition voltage control circuit, that is, the voltage generated by the addition voltage generation coil may be a voltage smaller than E _V / N and E _V. Since the withstand voltage of the circuit elements used in the voltage control circuit can be reduced, downsizing and cost reduction of these circuit elements can be achieved.

In addition, even if there is a capacitor that remains charged in the multiple voltage circuit when the screen of the cathode ray tube suddenly changes from "bright" to "dark", the charged charge of this capacitor is quickly discharged by the discharge circuit. Therefore, a voltage higher than a large reverse withstand voltage is not applied to a circuit element such as a transistor in the added voltage control circuit, and thus the circuit element can be sufficiently protected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
Waveform diagram of each part of the circuit shown in the figure, and FIG.
Operation waveform diagram of each circuit portion under the condition of e ₆ <0 when there is no transistor of FIG. 4, and FIG. 4 shows e ₆ <0 of the circuit of FIG. 1 in which the differentiation circuit and the second transistor are provided. Operating waveform diagrams of each circuit portion under conditions, FIGS. 5 to 7
FIG. 8 is an explanatory view of the operation of the multiple voltage circuit, FIG. 8 is an explanatory view showing the discharge path of the discharge circuit, FIG. 9 is an explanatory view showing the current flow of the discharge circuit during the scanning period, and FIG. 10 is a conventional high voltage. FIG. 11 is a circuit diagram showing a generating circuit, FIG. 11 is a half sectional view of a flyback transformer using a laminated type high voltage coil, FIG. 12 is a connection diagram of the high voltage coil shown in FIG. 11, and FIG. 13 is an anode of a cathode ray tube. Fig. 14 is a characteristic comparison diagram comparing the relationship between the applied high voltage output voltage E _H and the high voltage current I _H when the high voltage coil is laminated winding and section winding, and Fig. 14 shows a means for dividing the high voltage output current I _H. 11 is a characteristic diagram showing the relationship between the high voltage output voltage E _H and the high voltage current I _H of the circuit of FIG. 1 ... Horizontal deflection output circuit, 2 ... Flyback transformer, 3 ... Reference voltage generation circuit, 4 ... Horizontal output transistor, 5 ... Damper diode, 6 ... Resonant capacitor, 7 ... Horizontal deflection coil, 8 ...... S-shaped correction capacitor, 9 ...... Voltage detector, 10 ...... Core, 11 ...... Low voltage coil, 12 ...... High voltage coil, 13 ...... Input power supply, 14 ...... High voltage rectifier diode, 15 ...... CRT, 16 ...... Anode, 17
…… Diode, 18 …… Fixed resistor, 19 …… Input tap, 20 …… Variable resistor, 21 …… Addition voltage generation coil, 22
…… Comparison amplifier, 23 …… Switching circuit, 24 …… Output tap, 25 …… Control voltage generating coil, 26 …… Rectifier, 27
…… Square wave output circuit, 28,29 …… Fixed resistor, 31 …… Integrator circuit, 32 …… Amplifier, 33 …… Clip circuit, 34 …… Drive transistor, 35,36 …… Diode, 37,38… …
Resistor, 39 …… Switching operation control circuit, 40 …… Capacitor, 41 …… Drive power supply, 42 …… Drive transformer, 43
...... Control transistor, 44 …… Primary coil, 45 …… Secondary coil, 46 …… Multiple voltage circuit, 47 …… First transistor, 48 …… Second transistor, 50 …… Differentiation circuit, 51 ・ ・ ・
… First diode, 52 …… Second diode, 53 ……
Third diode, 54 ... Inverting amplifier, 55 ... First capacitor, 56 ... Second capacitor, 57 ... Third capacitor, 58 ... Diode, 60 ... Discharge circuit, 61 ... Resistor Vessel, 62 ... diode.

Claims (1)

[Claims] 1. A high voltage generation circuit for boosting a flyback pulse applied from a horizontal deflection output circuit by a flyback transformer and applying a high voltage output voltage from a high voltage side of a high voltage coil constituting the transformer to an anode of a cathode ray tube. The added voltage generating coil wound around the core of the transformer to generate the added voltage and the added voltage generated by the added voltage generating coil are controlled to output a correction voltage that increases as the amount of drop of the high voltage output voltage increases. And a multiplying circuit which has a plurality of capacitors and diodes and which boosts the correction voltage from the adding voltage control circuit and adds the boosted output to the cathode of the cathode ray tube through the high voltage coil. , While the high voltage output current is flowing from the high voltage coil to the cathode of the cathode ray tube, High voltage generating circuit but which comprises an a discharge circuit for discharging electric charge of the capacitor that remain charged among capacitors of the multi-precision pressure circuit when sharply approximately zero.