JPH0681264B2 - High voltage generation circuit - Google Patents

Description

The present invention relates to a high voltage generating circuit for stabilizing a high voltage output voltage applied to an anode of a cathode ray tube by so-called pulse width control.

[Prior Art] FIG. 8 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 through the diode 17 as shown in FIGS. 8 to 10, 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, it is sufficient to consider only the DC potential difference in the insulation treatment of each layer winding, 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. 11, 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. 11, the high voltage current I _H flowing from the coil 12 to the anode 16 of the cathode ray tube 15 abruptly fluctuates in the range of 0 to 200 μA simply by making the high voltage coil 12 into a multi-layer winding (multilayer winding). However, an unfavorable phenomenon occurs. Therefore, in recent years, as shown in FIG. 8, a fixed resistor is provided between the high voltage output side (the anode side of the cathode ray tube 15) and the ground.
18 and the variable resistor 20 are arranged in series, and about 10% of the high voltage output current 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. 11 and 12,
If a variable setting range of the high voltage current I _H is set to a range of 0～1000Myuei, if not taken shunt means high-voltage current I _H, the output impedance Z ₀₁ is Z ₀₁ from FIG. 11 = (27-
25) KV / 1000μA = 2MΩ. On the other hand, if I _H shunting means is taken, the output impedance Z ₀₂ will be Z ₀₂ = (26.1−24.9) KV / 1000 μA = 1.2 MΩ from FIG.
This means that the output impedance has been improved considerably.

[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 achieve a large reduction in output impedance without power loss, in other words, stabilization of a high voltage with respect to a change in high voltage current. It is to provide a high-pressure generator capable of

[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 flightback 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. An additional voltage generation coil that is wound around the core of the back transformer and generates an additional voltage, and a reference that generates a triangular wave voltage with a constant waveform whose peak value is from the start point of the blanking period to the end point of the rising blanking period. A voltage generating circuit, a voltage detecting section for detecting a change in the high voltage output voltage by extracting the high voltage output voltage or the high voltage output current, and comparing the detection voltage detected by the voltage detecting section with the triangular wave voltage of the reference voltage generating circuit. When the triangular wave voltage exceeds the detection voltage, a comparison amplifier that outputs a rectangular control signal and When it is between the voltage at the start point of the wave and the voltage at the peak value, the gate is opened in the section from the rising position of the rectangle to the end point of the blanking period in the control signal applied from the comparison amplifier. A switching circuit that applies the generated added voltage to the high-voltage coil side of the flyback transformer, and the switching circuit in a short section of the peak position of the pulse waveform of the added voltage when the detected voltage is lower than the voltage at the starting point position of the triangular wave. And a switching operation control circuit for opening the gate of the switch.

[Action]

In the present invention configured as described above, when the high voltage output current flows to the anode of the cathode ray tube and the high voltage output voltage decreases, the voltage detected by the voltage detecting unit also decreases. Therefore, when comparing the detected voltage and the triangular wave voltage with the comparison amplifier, when the detected voltage is between the voltage at the starting point position and the voltage at the peak position of the triangular wave, the detected voltage is reduced by the level of the detected voltage. The section of the triangular wave voltage that exceeds is increased. Along with this, the width of the rectangle of the control signal output from the comparison amplifier increases, the period for opening the gate of the switching circuit increases, and the added voltage applied to the high voltage coil also increases, thus stabilizing the high voltage output voltage. Control is performed in the direction.

Further, when the detected voltage becomes lower than the voltage at the starting point position of the triangular wave, the switching operation control circuit is driven to cause the switching circuit to open the gate in a section where the peak position of the added voltage pulse waveform is short. As a result, the maximum wave height component of the added voltage pulse is efficiently added to the high voltage coil, and control is performed in a direction to stabilize the high voltage output voltage.

〔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
The comparison amplifier 22, the switching circuit 23, and the switching operation control circuit 39 are provided.

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 VRs 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 , VRs 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. . 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 first 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 blanking period Tr, sets 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 second input terminal of the comparator 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 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, a high voltage current flows to the anode 16.
I _H flows, and due to the internal impedance of the high voltage generator,
The high-voltage output voltage E _H drops, and the voltage e ₆ detected by the voltage detection unit 9 also drops accordingly. When the detection voltage e ₆ drops, the detection voltage e ₆ is changed to an integration circuit as shown in FIG. 2 (c).
Since it falls below the peak position of the triangular wave voltage e ₅ generated in 31, the triangular wave voltage e ₅ changes the detection voltage e ₆ to the detected voltage e ₆ in the interval of Δt ₁ of the blanking period and the interval of Δt ₂ beyond the blanking period. Exceed. 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 detected voltage e ₆ , that is, the high-voltage output voltage E _H decreases, Δt (where Δt =
The section of Δt ₁ + Δt ₂ ) becomes wider, and the section of 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, Invert the waveform of e ₇ at inverting amplifier 54 e _'8 of the waveform (FIG. 2 (e))
However, since the scanning period T _S is in the period of t _{4 to} t ₅ and t _{9 to} t ₁₀ , the control transistor 43 is cut off as described later, and as a result, the waveform of e ₈ is changed. Voltage is applied to the base of the drive transistor 34) Hereinafter, the circuit operation when the output voltage e ₈ thereof is applied to the switching circuit 23 will be described below.

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 detected 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 e ₆ of e ₅ should cross. Therefore, the control signal e ₇ pulse is not generated,
e ₇ becomes 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 as follows by providing the switching operation control circuit 50 including the first transistor 47, the second transistor 48 and the differentiating circuit 50. In FIG. 3, first, as a pre-stage for explaining the operation of the switching operation control circuit 50, first,
The waveforms of the respective circuit parts when only the transistor 47 is provided are shown under the condition of e ₆ <0. Under the condition of e ₆ <0, a pulse e ₉ (the voltage of which the scanning period has a positive voltage and the retrace line period has a zero voltage from the output end side of the fixed resistor 29 to the base side of the first transistor 47) FIG. 2 (i)) is 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, almost the same section as the pulse section of I ₂ ,
A pulse current I ₁ (third part) is applied to the collector side of the control transistor 43.
Figure (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,
In addition to the first transistor 47, a differentiating circuit 50 and a second transistor 48 are provided to form a switching operation control circuit 39.

FIG. 4 shows the waveform of each circuit portion under the condition of e ₆ <0 when the switching operation control circuit 39 is provided. Under this condition of e ₆ <0, the differentiating circuit 50 differentiates the output voltage e ₃ from the clipping circuit 33 and applies the differential output e ₁₃ shown in FIG. 4 (f) 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 of the waveform portion (slope portion) 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. In this way, the on position of the control transistor 43 is shifted by the differential output e ₁₃ , and the peak of the waveform of I ₁ and the peak of the waveform of e ₁ are made to coincide with each other.
When the general drive transformer 42 is used, a large added voltage e ₁₂ can be applied to the high voltage coil via the multiple voltage circuit by turning on the drive transformer 42, and the drive transformer 42 is increased in size. Various problems such as heat generation can be effectively eliminated.

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.

By the way, in the circuit operation, it may be necessary to flow the high-voltage output current even when the high-voltage output voltage E _H becomes larger than the correction range. In this embodiment, the anode is on the ABL side and the cathode is the first side. The object is achieved by arranging the diode 58 connected to the connection part between the cathode of the diode 51 and the anode of the second diode 52.

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 that if the drop amount of E _H is large. also becomes longer time that much open gate, the E voltage e ₁₂ is also increased to be added to _H, it causes the circuit to operate in the direction of certain of the E _H. 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. in that since the gate of the short pulse width of I ₁ by the control transistor 43 in which is controlled to open, the control transistor even though the on time is short of 43 large voltage e ₁₂ multidigit pressure circuit 4
Since it is applied to the high voltage coil 12 via 6, a sharp decrease in the high voltage output voltage E _H is effectively prevented. Also,
In this case, the control transistor 43 is not turned on throughout the blanking period Tr, but the second transistor 48 is turned on.
Since the control transistor 43 is turned off during the period when is turned on, the section in which the control transistor 43 can be turned on to the maximum extent is limited to Δt ₃ in FIG. Control transistor like this
By limiting the 43 on-period of the short, it is possible to reduce the heat generated from the transistor 43 and the drive transformer 42, also savings in power consumption can be achieved, further, the E _H by small drive transformer 42 capacity The stabilization purpose can be sufficiently achieved.

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 boosted by the drive transformer 42 and added, the withstand voltage of the control transistor 43 does not have to be a super withstand voltage, and a product with a withstand voltage of about 1500 V can sufficiently achieve the purpose 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.

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, a double voltage circuit is used as the multiple voltage circuit 46, but it may be constituted by a circuit of different voltage doubles such as triple pressure, quadruple pressure, etc. The multiple voltage circuit 46 may be omitted.

Further, in the circuit shown in FIG. 1, the high voltage coil 12 may be formed into a multi-layer laminated winding. At this time, as shown in FIG. 8, 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 current and indirectly obtain the detection voltage e _6. Good. In this case, the extracted high voltage output current is
It is introduced from the side to the comparison amplifier 22 via a resistor, and some circuit changes are required.

〔The invention's effect〕

As described above, according to the present invention, the drop of the high voltage output voltage E _H due to the flow of the high voltage current I _H is opened by the control current having the pulse width corresponding to the drop, and the added voltage is changed to the high voltage output coil. Since the added voltage corresponding to the voltage drop is replenished to the high voltage coil, the high voltage output voltage can be stabilized and the screen distortion can be effectively prevented. Since the output impedance of the high voltage generation circuit can be made extremely small, it is possible to sufficiently meet the demand for higher definition of image quality. Further, when the high voltage output voltage drops too much and the detected voltage becomes lower than the voltage at the starting point position of the triangular wave during the stabilization operation of the high voltage output voltage, the switching operation control circuit operates and the peak portion of the added voltage is short. Since the gate is opened in the switching circuit in the section, a large voltage component of the peak portion of the added voltage is effectively added to the high voltage coil side, which can prevent a rapid decrease in the high voltage output voltage. In addition, by controlling the period of opening the gate of the switching circuit to a short time width, the operating time width of the gate circuit can be reduced, which can reduce heat generation from each circuit element of the gate circuit and also reduce power consumption. Can be achieved.

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, according to the present invention, the pulse width can be controlled within the blanking period with a small circuit configuration, and since the pulse width control is performed within the blanking period, there is no concern that the switch noise of the switching circuit appears on the screen. In addition, heat generation of the transistor or the like used for switch control can be reduced.

Further, according to the present invention, 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 an alternating manner.

Furthermore, the ground of the switching circuit of the present invention is not always
Since it is not necessary to use the line on the ABL side, the degree of freedom in circuit design can be increased.

[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 a diagram for explaining the operation of the multiple voltage circuit, Fig. 8 is a circuit diagram showing a conventional high voltage generating circuit, Fig. 9 is a half sectional view of a flyback transformer using a laminated type high voltage coil, and Fig. 10 is 9
The connection diagram of the high-voltage coil shown in the figure, and Fig. 11 shows the comparison of the relationship between the high-voltage output voltage E _H and the high-voltage current I _H applied to the cathode of the cathode-ray tube when the high-voltage coil is laminated and section winding. Figure, FIG. 12 is a characteristic diagram showing the relationship between the high voltage output current I high output voltage of the circuit of Figure 8 that shunt means are provided in _H E _H and the high-pressure current I _H. 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, 30 …… Transistor, 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 ... Driving power supply, 42 ...
… Drive transformer, 43 …… Control transistor, 44 ……
Primary coil, 45 …… Secondary coil, 46 …… Multiple voltage multiplying circuit, 47
...... First transistor, 48 …… Second transistor,
50 …… differential circuit, 51 …… first diode, 52 …… second
, 53 ... Third diode, 54 ... Inverting amplifier, 55 ... First capacitor, 56 ... Second capacitor, 57 ... Third capacitor, 58 ... 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. An added voltage generator coil that is wound around the core of the transformer and that generates an added voltage, and a reference voltage that generates a triangular wave voltage with a constant waveform whose peak value is from the start point of the blanking period to the end point of the rising blanking period. The generation circuit, a voltage detection unit for detecting the change in the high voltage output voltage by extracting the high voltage output voltage or the high voltage output current, and the detection voltage detected by the voltage detection unit and the triangular wave voltage of the reference voltage generation circuit are compared. A comparison amplifier that outputs a rectangular control signal in a section where the triangular wave voltage exceeds the detection voltage; When the voltage is between the fixed voltage and the peak value voltage, the addition signal generated by the addition voltage generating coil is opened in the section from the rising position of the rectangle to the end point of the blanking period in the control signal applied from the comparison amplifier. A switching circuit that applies a voltage to the high-voltage coil side of a flyback transformer, and a gate to the switching circuit when the detected voltage is lower than the voltage at the starting point position of the triangular wave, at a short section of the peak position of the pulse waveform of the added voltage. And a switching operation control circuit for opening the high voltage generation circuit.