JPH0586113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high voltage generation circuit provided with a stabilizing circuit for high voltage output voltage applied to the anode of a cathode ray tube.

[Conventional technology]

FIG. 3 shows a conventional high voltage generation circuit. This high voltage generation circuit includes a horizontal deflection output circuit 1,
It is equipped with two flyback transformers.

The horizontal deflection output circuit 1 includes a horizontal output transistor 4, a damper diode 5, a resonant 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 and performs a switching action, and the damper diode 5
A sawtooth wave current is applied to the horizontal deflection coil 7 in cooperation with the horizontal deflection coil 7. On the other hand, the resonant capacitor 6 and the horizontal deflection coil 7 generate flyback pulses by their resonant action, which are applied to the flyback transformer 2.

The flyback transformer 2 consists of a core 10 wound with a low voltage coil 11 and a high voltage coil 12. One end of the low voltage coil 11 is connected to the collector side of the horizontal output transistor 4, and the coil 1 is connected to the collector side of the horizontal output transistor 4.
The other end of 1 is connected to an input power source 13. The high voltage side of the high voltage coil 12 is connected to the anode 16 of the cathode ray tube 15 via the high voltage rectifier diode 14, and the other end of the coil 12 is connected to the anode 16 of the cathode ray tube 15.
(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 output voltage) to the anode 16 of the cathode ray tube 15.

Generally, the high voltage coil 12 is wound in multiple layers through diodes 17 as shown in FIGS. 3 to 5, and the coil between each layer is wound with the same number of turns, the same winding width, and the same winding pitch, and each layer If the winding end of the coil and the winding start of the next layer are made to have the same polarity using the diode 17, the potential difference between the coils of each layer becomes zero in terms of alternating current. Therefore, the insulation process between each layer only needs to consider the DC potential difference, and there is no need to consider heat generation due to dielectric loss, making the insulation process easy.

Furthermore, by winding the high voltage coil 12 in multiple layers as described above, the insulation distance between the low voltage coil 11 and the high voltage coil 12 can be made smaller compared to other section-wound coils, so the finished outer diameter of the outermost layer of the coil can also be reduced. Can be made smaller. As a result, as shown in FIG. 6, there is an advantage that the leakage inductance of the high-voltage coil 12 can be reduced.For this reason, a flyback transformer 2 in which the coil 12 is of a multi-layer winding type is widely used.

However, as shown in Fig. 6, the high voltage coil 1
If only the coil 2 is wound in multiple layers, the high voltage current flowing from the coil 12 to the anode 16 of the cathode ray tube 15 will be 1 _H.
changes rapidly in the range of 0 to 200 μA, causing an undesirable phenomenon. Therefore, in recent years, as shown in FIG. 3, 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 _IH is about
A 10% current is shunted to prevent sudden fluctuations in the high-voltage output current, as shown in FIG.

That is, in the characteristic diagrams shown in FIGS. 6 and 7, the variable setting range of high voltage current I _H is 0 to
Assuming that it is set in the range of 1000 μA, if no means of diverting the high voltage current I _H is taken, the output impedance Z ₀₁ will be Z ₀₁ = (27-25) kv/ from Figure 6.
1000μA = 2MΩ. On the other hand, if _IH shunt means were taken, the output impedance Z ₀₂ would become Z ₀₂ = (26.1-24.9) kv/1000 μA = 1.2 MΩ, as shown in Figure 7, resulting in a fairly significant improvement in the output impedance. It turns out.

[Problem that the invention seeks to solve]

However, today, cathode ray tubes
There is an increasing demand for higher definition in the image quality of 5, and it is desired to further reduce the output impedance. Moreover, when lowering the output impedance, a means that does not involve power loss is strongly desired, and as described above, the method of dividing _IH through the fixed resistor 18 and the variable resistor 20 satisfies this demand. They are no longer able to respond to all demands and are no longer accepted by the market.

The present invention has been made in view of the above circumstances,
The purpose is to provide a high voltage generator that can significantly reduce output impedance without causing power loss, in other words, stabilize high voltage against changes in high voltage current.

[Means for solving problems]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention boosts the flyback pulse applied from the horizontal deflection output circuit with a flyback transformer, and applies the high voltage output voltage from the high voltage side of the high voltage coil constituting the transformer to the anode of the cathode ray tube. It is wound around the core of the back transformer and is approximately 1/n (n
is an integer); an addition voltage generation coil that generates a pulse voltage; a voltage detection section that detects a high voltage output voltage;
a differential amplifier that outputs a voltage signal corresponding to the change in the detected voltage detected by the voltage detector; an addition voltage control circuit that outputs a pulse voltage obtained by multiplying the voltage generated by the addition rate; and an addition voltage control circuit that increases the output voltage from the addition voltage control circuit by approximately n times and applies the multiplied pulse voltage to the high voltage coil. It is characterized by having a multi-voltage circuit that applies to the low voltage side;

[Effect]

In the present invention configured as above,
An additional voltage of ΔE _H ×1/n is generated in the additional voltage generating coil, where ΔE _H is the voltage change when the high voltage output current I _H is changed to the full variable setting range. In this state, a high voltage current I _H flows through the anode of the cathode ray tube, and when the high voltage output voltage E _H decreases,
The voltage drop is detected by the voltage detection section, and the differential amplifier sends a signal corresponding to the voltage drop to the addition voltage control circuit. The addition voltage control circuit determines an addition rate suitable for stabilizing the high voltage output voltage E _H according to the signal value sent from the error amplifier, and adds the addition rate to the addition voltage generated by the addition voltage generation coil. Similarly, the added output voltage is applied to the multiplier circuit. The multiplier circuit increases the added output voltage by n times.

As a result, a voltage that is a desired multiple of the added output voltage, that is, a voltage corresponding to the drop in the high-voltage output voltage, is added to the high-voltage output voltage via the multiplier circuit, and the high-voltage current _IH flows. The resulting decrease in the high voltage output voltage _EH is compensated for, thereby stabilizing the high voltage output voltage.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. In the description of this embodiment, circuit parts that are the same as those of the conventional example are denoted by the same reference numerals, and redundant explanation thereof will be omitted.

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

The characteristics of this embodiment that differ from the conventional example are that an addition voltage generating coil 21, an error amplifier 22 functioning as a differential amplifier, an addition voltage control circuit 23,
A voltage detection section 19 is provided.

The addition voltage generating coil 21 is wound around the core 10 of the flyback transformer 2, and the output end side (winding end side) of the coil 21 has a first tap 24 and a second tap 25. It is provided. This _first tap _{24 is approximately ΔE}
The second tap 25 is provided at a coil winding position that generates a voltage (additional voltage) of provided at the location. The amount of winding of this second tap 25 is the winding length that compensates for the voltage drop of the resistor 26 connected to the second tap 25, that is, the voltage corresponding to the voltage drop of the resistor 26 is set between both taps. The winding length is set to be generated between 24 and 25.

On the other hand, one end of a fixed resistor 28 is connected to the high voltage side of the high voltage coil 12 (the cathode side of the high voltage rectifier diode 14), and the other end of the resistor 28 is connected to a variable resistor VR _F , a fixed resistor 29, variable resistor VR ₂ ,
The fixed resistor 30 and the variable resistor VR ₁ are connected in series in this order to constitute the voltage detection section 19 for the high voltage output voltage _EH . The variable resistor VR ₁ is connected to the low voltage side (winding start side) of the addition voltage generating coil 21, and its connection portion communicates with ABL.

The variable resistor VR ₁ detects the high output voltage E _H and applies this detected voltage e _H to the positive terminal of the error amplifier 22 . On the other hand, the positive side of the reference power supply 32 is connected to the negative side terminal of the error amplifier 22.
A reference voltage e _S is applied from the power supply 32 to the negative terminal. Note that the negative side of the power supply 32 is connected to the common connection portion between the variable resistor VR ₁ and the low voltage side and ABL side of the addition voltage generating coil 21.

The error amplifier 22 has a reference voltage e _S and a detection voltage e _H
and outputs an output voltage e _e corresponding to the difference e _H −e _S. In this example, the variable resistor is set so that the detected voltage e _H becomes equal to the reference voltage e _S when the output current I _H changes the maximum within the set variable range (I _H = I _HM) .
Adjusting the resistance value of VR ₁ .

The addition voltage control circuit 23 includes the first transistor 3
3, a diode 34, a second transistor 35, and a resistor 26. first transistor 33
The base side of the transistor 33 is connected to the output terminal of the error amplifier 22, the emitter side of the transistor 33 is connected to the low voltage side of the addition voltage generating coil 21, and the collector side of the transistor 23 is connected to the cathode side of the diode 34. ing. The anode side of the diode 34 is connected to the base side of a second transistor 35, and the collector side of the second transistor 35 is connected to the first tap 24 of the addition voltage generating coil 21. Furthermore, the same coil 21
The resistor 2 is connected between the second tap 25 and the base of the resistor 2.
6 is interposed, and the emitter of the second transistor 35 is connected to the input side of a multiplier circuit 36.

This multiplier circuit 36 is composed of first to fourth diodes 37, 38, 39, 40 and first and second capacitors 41, 42, respectively. The anode side of the first diode 37 is connected to the emitter side of the second transistor 35, and the cathode side of the first diode 37 is connected to the second transistor 35.
The anode side of the diode 38 is connected to the anode side of the diode 38, and the cathode side of the diode 38 is connected to the anode side of a third diode 39 to form a series connection body of diodes, and the cathode side of the third diode 39 is connected to the high voltage coil. It is connected to the low pressure side of 12.

Further, one end of the first capacitor 41 is connected to a common connection between the emitter of the second transistor 35 and the anode of the first diode 37, and the other end of the capacitor 41 is connected to the second diode 38. and the anode side of the third diode 39. On the other hand, the fourth diode 40 and the second capacitor 42 are connected in parallel, and one end side of the parallel circuit (the cathode side of the fourth diode 40) is connected to the first diode 37 and the second diode 38. The other end of the parallel circuit is connected to the emitter side of the first transistor 33.

This embodiment is configured as described above, and its operation will be explained below.

First, when the high voltage current I _H flowing to the anode side of the CRT cathode ray tube reaches the maximum specified value I _HM in the operating range,
The high voltage output voltage E _H decreases, but at this time, as mentioned above, the voltage of the detection signal entering the error amplifier 22
Since e _H and the reference voltage e _S become equal, the output voltage e _e from the error amplifier 22 becomes zero and the first transistor 33 is cut off.

On the other hand, at this time, between the low voltage side end of the addition voltage generating coil 21 and the first tap 24, e _N2 =Δe×N ₂
pulse voltage is generated.

However, Δe is the voltage generated per turn of the coil, and N ₂ is the voltage between the low voltage side end of the coil 21 and the first
This is the number of turns of the coil between taps 24. The waveform of this e _N2 pulse voltage is expressed as shown in FIG. 2, and the positive portion of this waveform diagram corresponds to e ₀ .

By the way, when the first transistor 33 is cut off, the voltage e ₀ is applied to the collector of the second transistor 35. At the same time, a voltage slightly higher than the voltage _e0 is applied from the second tap 25 side to the base side of the second transistor 35 through the resistor 26, and to the emitter side of the second transistor 35.
A positive pulse voltage of e ₀ is generated. In other words, the addition voltage control circuit 23 sets the addition rate to 1 (100%), multiplies the addition voltage e ₀ generated by the addition voltage generation coil 21 by the addition rate 1, and outputs the resulting output voltage e ₀ to the multiplier voltage circuit. Add to 36.

This addition voltage control circuit 23 controls the high voltage output voltage E _H
The addition rate is determined to compensate for the drop in EH, that is, to stabilize _EH . In other words, when the high voltage output current I _H changes fully from 0 to I _HM in the variable setting range, and if the output impedance of the voltage output circuit is Z ₀ , the voltage drop ΔE _H is ΔE _H = I _HM × Z ₀ It is expressed as ΔE _H =ne ₀ (n is an integer)
When , the high voltage output voltage E _H becomes stable.

That is, when ΔE _H =ne ₀ , the addition voltage generating coil 21 generates an addition voltage of ΔE _H ×1/n=e ₀ . This added voltage is then applied to the added voltage control circuit 2.
As mentioned above, the addition rate 1 is multiplied by 3,
A voltage of e ₀ ×1=e ₀ is applied to the multiplier circuit 36.

This multiplier circuit 36 increases the added voltage by a factor of n. That is, during the retrace period T _r of the deflection period, a current flows along the path indicated by the solid line a in FIG. 1, and e ₀ is generated in the second capacitor 42 of the multiplier circuit 36.

Next, during the scanning period T _S , a reverse leakage current flows through the second transistor 35 formed of a bipolar transistor or the like, so that the current flows along the path shown by the dotted line in FIG. 1 . As a result, a voltage of e ₀ +e ₂ is generated across the first capacitor 41 . However, as shown in FIG. 2, e ₂ is the voltage of the negative portion of the pulse voltage generated by the addition voltage generating coil 21.

Then, when the retrace period T _r is entered again, a current flows along the path shown by the dashed line C in FIG. 1, and a voltage of 2e ₀ +e ₂ is applied to the low voltage side of the high voltage coil 12. This e ₂ is very small compared to e ₀ , so the multiplier circuit 36 of this embodiment functions as a double voltage circuit with n=2.

As mentioned above, high voltage output voltage E _H drop ΔE _H (2e ₀ )
is compensated by the voltage 2e ₀ applied from the multiplier circuit 36, and stabilization of E _H is achieved.

Next, when the high voltage output current I _H is 0, no voltage drop occurs in E _H , so the high voltage output voltage E _H increases by Z ₀ ×I _HM compared to when I _H = I _HM . Therefore, the detection voltage e _H entering the error amplifier 22 is the reference voltage e _S
, and the voltage e _e corresponding to the value of e _H −e _S
is output as an output signal.

As a result, the first transistor 33 becomes completely conductive, so the second transistor 35 is cut off, and the compensation voltage added to the high voltage output voltage E _H becomes zero.

The above results can be summarized as follows. In other words, if the high voltage output voltage when the high voltage output current I _H is 0 is E _HO , the high voltage output voltage E _H when I _H = I _HM is E _H = E _HO − _{I HM} ×Z ₀ +ne ₀ = Become E _HO . Also, I _H
When = 0, E _H = E _HO , and both high voltage output voltages are equal.

Next, even when I _H is between 0 and I _HM , the addition voltage control circuit 23 determines the addition rate so that the high voltage output voltage E _H is constant according to the magnitude of the detected voltage e _H. , E _H is stabilized. That is, when e _H is large (small), the output voltage e _e from the error amplifier 22 also becomes large (small), and when e _H is large (small), the collector voltage of the first transistor 33 becomes small ( Accordingly, the voltage on the emitter side of the second transistor 35 also decreases (increases), and the voltage applied to the voltage multiplier circuit 36 also decreases (increases). In other words, the drop in the high voltage output voltage E _H is large (e _H
When the drop in E _H is small (e H is small), the compensation voltage applied to E _{H becomes large, and when the drop in E H} is small (e _H is large), the compensation voltage becomes small, and the circuit operates to keep the high voltage output voltage E _H constant. As a result, _EH is stabilized.

By the way, in general, a compensation voltage of about 2KV at maximum is required to stabilize the high voltage output voltage _EH . If the multiplier circuit 36 as in this embodiment
If not provided, the reverse breakdown voltage of the transistors 33 and 35 must be set to 2KV or more. but,
Such high-voltage transistors are not commonly used, and specially manufactured transistors are extremely expensive and inconvenient. On the other hand, as in this embodiment, an n-times multiplier circuit 36 is provided downstream of the addition voltage control circuit 23.
By providing , it becomes possible to reduce the reverse breakdown voltage of the transistors 33 and 35 to 1/n, and the purpose can be sufficiently achieved with a general-purpose transistor.

Further, according to this embodiment, one end of the resistor 26 connected to the base side of the second transistor 35 is connected to the wound end of the addition voltage generating coil 21, that is, the second tap 25. The advantage is that the voltage on the base side of the transistor 35 can be increased to a voltage equal to the voltage on the collector side, and the transistor 35 can be operated over a wide voltage range up to its full reverse breakdown voltage. .

Further, in this embodiment, the second transistor 35
Since the structure is configured to allow reverse leakage current to flow, the normally required diode 43 can be omitted. Furthermore, in this embodiment, since the output of the multiplier circuit 36 is applied as a pulse component to the high voltage coil 12, there is an advantage that the capacitor 44 required in a general multiplier circuit can be omitted. .

Furthermore, in this embodiment, the first transistor 3
A diode 34 is provided on the collector side of the transistor 3 and the base side of the second transistor 35.
Since the cathode side of the first transistor 33 is connected to the collector side of the first transistor 33, the _first
Current does not flow backwards from the emitter side to the collector side of the first transistor 33, and therefore, the inconvenience that the reverse current flows to the first transistor 33 and causes power loss does not occur.

Note that the present invention is not limited to the above-mentioned embodiments, and may take various other embodiments. For example, although the high voltage generation circuit of this embodiment serves both as a flyback pulse generation circuit and a horizontal deflection output circuit, the horizontal deflection output circuit may be separated, and in that case, the horizontal deflection coil 7 and the S-shaped The correction capacitor 8 can be omitted. Further, in the above embodiment, the high voltage coil 12 is not wound in a laminated manner as shown in FIG. 1, but the coil 12 may be divided into 12 pulses and wound in a laminated manner in multiple layers. In this case, as shown in FIGS. 3 to 5 of the conventional example, a diode 17 is interposed between the separately wound coils of each layer.

〔Effect of the invention〕

Since the present invention is constructed as described above, the high output voltage can be stabilized, and screen distortion and focus deterioration can be effectively prevented. Furthermore, the output impedance of the voltage generating circuit can be made extremely small, which satisfies the demand for higher definition image quality.

Furthermore, since the adder voltage generating coil is wound around the core of the flyback transformer, so-called AC insulation can be achieved for the entire circuit with the core of the flyback transformer as the boundary line. A multi-voltage circuit that doubles the voltage by n times is provided on the low-voltage side of the high-voltage coil of a flyback transformer, an addition voltage control circuit is provided upstream of this multiplication voltage circuit, and an addition voltage generation coil is further provided upstream of the multiplication circuit. Therefore, for example, if the maximum pulse voltage required to compensate for the drop in the high voltage output voltage (maximum change in the high voltage output voltage) is ΔE _H , the pulse voltage generated by the addition voltage generating coil is 1/n of that.
Therefore, the voltage applied from this addition voltage generating coil to circuits such as the addition voltage control circuit interposed between the multiplier circuit is also small, and the circuit elements used in these circuits are specially designed. It is possible to significantly reduce the cost and size of the circuit elements used by using general-purpose, low-voltage devices instead of the high-voltage devices specified in the specifications.

Furthermore, the present invention generates a pulse voltage with an addition voltage generating coil, and the addition voltage control circuit multiplies the generated pulse voltage by an addition ratio and applies the output voltage as it is to the multiplier circuit in the form of a pulse voltage waveform.
The multiplier circuit doubles the input pulse voltage by n times and applies it to the high-voltage coil in the same pulse voltage state.In other words, it performs signal processing such as rectification and smoothing on the pulse voltage generated by the addition voltage generation coil. Since the configuration is such that the signal is processed in the waveform form of the generated pulse voltage as it is, the signal processing is extremely easy, and there is no need for circuits such as circuits to rectify and smooth the pulse voltage or a dedicated power supply to drive these circuits. Since it is not necessary at all, it is possible to greatly simplify the circuit configuration, and at the same time, it is possible to reduce the circuit cost and downsize the circuit device.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a waveform diagram of the voltage generated by the addition voltage generating coil, and Figure 3 is a circuit diagram showing a conventional high voltage generating circuit.
Fig. 4 is a half-sectional view of a flyback transformer using a laminated type high-voltage coil, Fig. 5 is a wiring diagram of the high-voltage coil shown in Fig. 4, and Fig. 6 shows the high-voltage output voltage E _H applied to the anode of the cathode ray tube. A characteristic comparison diagram comparing the relationship between the voltage and current I _H when the high-voltage coil has a _laminated winding and a section winding. FIG. 3 is a characteristic diagram showing the relationship between high voltage output voltage E _H and high voltage current I _H of . DESCRIPTION OF SYMBOLS 1... Horizontal deflection output circuit, 2... Flyback transformer, 4... Horizontal output transistor, 5... Damper diode, 6... Resonance capacitor, 7... Horizontal deflection coil, 8... S-shaped correction capacitor, 10... Core,
11...Low voltage coil, 12...High voltage coil, 13...Input power supply, 14...High voltage rectifier diode, 15...Cathode ray tube, 16...Anode, 17...Diode, 1
8... Fixed resistor, 20... Variable resistor, 21... Addition voltage generating coil, 22... Error amplifier, 23... Addition voltage control circuit, 24... First tap, 25... Second
tap, 26...Resistor, 28, 29, 30...Fixed resistor, 32...Reference power supply, 33...First transistor, 34...Diode, 35...Second transistor, 36...Multiplier circuit, 37... 1st diode, 38...2nd diode, 39...3rd diode, 40...4th diode, 41...1st diode
capacitor, 42... second capacitor, 43...
Diode, 44...capacitor.

Claims (1)

[Scope of Claims] 1. A high voltage generation circuit that boosts a flyback pulse applied from a horizontal deflection output circuit using a flyback transformer and applies a high voltage output voltage to the anode of a cathode ray tube from the high voltage side of a high voltage coil constituting the transformer, An additional voltage that is wound around the core of a flyback transformer and generates a pulse voltage that is approximately 1/n (n is an integer) for the change in high voltage output voltage when the high voltage output current changes over the variable setting range. a generating coil; a voltage detection section that detects a high voltage output voltage; a differential amplifier that outputs a voltage signal corresponding to a change in the detected voltage detected by the voltage detection section; a high voltage output based on the output signal of the differential amplifier. an addition voltage control circuit that determines an addition rate to stabilize the voltage and outputs a pulse voltage obtained by multiplying the addition rate by the voltage generated by the addition voltage generation coil; increasing the output voltage from the addition voltage control circuit by approximately n times; A high voltage generation circuit comprising: a multiplier circuit that increases the pulse voltage to the low voltage side of a high voltage coil; 2. The addition voltage control circuit consists of a first transistor, a second transistor, a diode, and a resistor, the base side of the first transistor is connected to the output terminal of the operational amplifier, the emitter side of the transistor is connected to the reference potential side, The collector side of the transistor is connected to the cathode of the diode, the anode of the same diode is connected to the base side of the second transistor, the emitter side of the transistor is connected to the input end of the multiplier circuit, and the collector side of the transistor is used to generate the addition voltage. The resistor is connected to the output end of the coil, and one end of the resistor is connected to the base of the second transistor, and the other end is connected to the output end of the addition voltage generating coil. A high voltage generation circuit according to claim 1, characterized in that: 3 On the output end side of the summing voltage generating coil, a first output tap is located at a winding position where a voltage approximately 1/n of the change in the high voltage output voltage is generated, and further winding is performed from the first output tap. A second output tap is provided at each winding position, and the collector side of the second transistor is connected to the first output tap, and the collector side of the second transistor is connected to the first output tap.
3. The high voltage generating circuit according to claim 2, wherein the output taps of the transistors are connected to the other ends of resistors whose one ends are connected to the bases of the transistors.