JPH0585103B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a deflection device for a television receiver, and more particularly to a deflection device provided with means for detecting a reduction occurring in a flyback transformer.

[Conventional technology]

As is well known, the deflection device of a television receiver is equipped with a flyback transformer for applying high voltage to the CRT cathode ray tube. By the way, if an abnormality such as a rear shot occurs in the high-voltage output coil of this flyback transformer, there is a risk of burnout of the receiver or fire. Therefore, in order to avoid such a danger, recent deflection devices are equipped with some kind of safety protection means, such as detecting an abnormality in the flyback transformer and turning off the power to the deflection device.

As a safety protection measure of this kind, JP-A-61-
The rarest detection device disclosed in Japanese Patent No. 24210 is known. As shown in FIGS. 5 and 6, this device has a high voltage side coil (secondary coil) 2 and a low voltage side coil (primary coil) 3 of a flyback transformer 1 wound on the same axis.
A pair of divided detection coils 4 and 5 are arranged at both ends of the low voltage side coil 3. Then, the detection signals of the detection coils 4 and 5 are added to the horizontal oscillation circuit 6 as a logical sum output (control voltage) V _CNT , and _the logic When the sum output becomes large,
The device automatically determines that the high-voltage side coil 2 is in a rare short state, and attempts to stop the oscillation operation of the horizontal oscillation circuit 6.

[Problem that the invention seeks to solve]

Generally, in the case of a flyback transformer, it is desirable that the distance between the high voltage side coil 2 and the low voltage side coil 3 be as close as possible in order to increase the degree of magnetic coupling. On the other hand, from the viewpoint of insulating the coils 2 and 3, it is necessary to ensure the minimum required insulation distance between the coils 2 and 3.

However, in the conventional deflection device, since the detection coils 4 and 5 are interposed between the high voltage side coil 2 and the low voltage side coil 3, the distance between the two coils 2 and 3 becomes too wide. In addition to deteriorating the magnetic coupling, there were problems in that it was not possible to secure the minimum necessary insulation distance between the two coils.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to prevent deterioration of the magnetic coupling of a flyback transformer, and to reduce the necessary minimum distance between the high-voltage side coil and the low-voltage side coil. It is an object of the present invention to provide a deflection device that can secure an insulation distance of 100 Ω and moreover reliably detect not only the high-voltage side coil but also the rare short of the low-voltage side coil.

[Means for solving problems]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides a horizontal drive circuit for horizontal scanning driving of a cathode ray tube;
a flyback transformer that boosts the output of the horizontal drive circuit and applies the output voltage to the anode of the cathode ray tube; a fuse connected directly or indirectly to the low voltage side coil of the flyback transformer; a fuse blowing power supply that supplies a blowing current to the fuse; a ratio detection circuit that detects an alternating current component flowing in the low voltage side coil of the flyback transformer and outputs a direct current voltage corresponding to the magnitude of the current value; A gate circuit that opens a gate when the output voltage of the detection circuit exceeds a reference value, causes a blowing current to flow directly from the fuse blowing power source, blows the fuse, and blocks voltage application to the low voltage side coil of the flyback transformer. It is characterized by having and;

[Effect]

In the present invention configured as above,
When a short circuit occurs in the low voltage side coil or high voltage side coil of a flyback transformer, the alternating current flowing to the low voltage side coil increases. Therefore, in response to this increase in current, the DC voltage output from the rarest detection circuit also increases, and as a result, this DC voltage value exceeds the voltage reference value given to the gate circuit in advance, causing the gate of the gate circuit to close. be opened. Then, a fusing current flows from the fuse blowing power source to the fuse directly or indirectly connected to the low voltage side coil, and the fuse is blown. By blowing out this fuse, the input of the drive voltage to the low voltage side coil is cut off, thereby achieving danger prevention by the rear shot.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In the order of explanation, first, before describing a specific example, the background of the present invention will be described.The present invention provides a method for reducing the low voltage side coil of a flyback transformer when a short circuit occurs in the low voltage side coil or the high voltage side coil of the flyback transformer. The aim is to detect rare shorts by focusing on the fact that the alternating current component flowing through them increases in the following way, and to prevent the danger thereof.

That is, when a reduction per turn occurs in, for example, the high-voltage side coil of the flyback transformer due to a manufacturing error, the equivalent circuit of the deflection circuit can be expressed as shown in FIG.
However, the leakage inductance of the high voltage side coil 25, the distributed capacitance, and the resistance within each element are ignored.

In the figure, C _O is the total resonance capacitance converted to the low voltage side coil side (primary coil side), which is affected by the occurrence of rare short, and L ₁ is the total resonance capacitance of the low voltage side coil 23 of the flyback transformer when it is normal. It is inductance.

At this time, L ₁ =A×(N ₁ ) ² (1) where A is a constant and N ₁ is the number of turns of the low voltage side coil 23.

Therefore, the inductance L _X ′ per turn of ^the flyback transformer is _L , L _X ′=L ₁ ×N ² /(N ₁ ) ² ...(3) This _L L _X is converted into N ₁ turn of the low voltage side coil 23.

∵L _X = ₍ ^N _{1 )} ² ×L
i _B is: i _B = t×E _B /L ₁ '...(5) (where t is time, E _B is the voltage of the input power supply 24,
L ₁ ′ is the primary inductance when a rare short occurs. ) Then, L ₁ ′=(L ₁ ×L _X )/(L ₁ +L _X ) ……(6).

Furthermore, if T _H is the deflection period, _TR is the retrace period, and T _S is the scanning period, then T _R = 〓 (L _O × C _O ) ^1/2 ... (7) However, L _O is the flyback period. The total inductance on the low voltage side when the low voltage side coil and the deflection coil of the transformer are connected in parallel T _H = T _R + T _S ...(8) Then, the current value between the peaks of the alternating current component i _B (I _BM (See Figure 3) is I _BM = T _S × E _B / L ₁ ′ = (T _H − T _R ) × E _B × (L ₁ + L _X ) / (L ₁ × L _X ) ……(9) Here So, T _R becomes smaller depending on the number of turns in the rarest, but since T _R is originally about 15% of T _H , assuming that T _H − T _R = T _S ′ = constant,
Equation (9) is I _BM = T _S ′×E _B (L ₁ +L _X )/(L ₁ ×L _X ) = (T _S ′×E _B )/L ₁ × (1+L ₁ / _L (10) becomes.

Inserting the relationship in equation (4) into equation (10), I _BM = (T _S ′×E _B )/L ₁ ×2, and _IBM becomes approximately twice as large as in a steady state. However, in reality, it does not double due to the resistance of the rarest coil part, but as shown in the above equation, _IBM increases due to the occurrence of rarest coils, and this
An increase in I _BM also occurs when the low-voltage side coil is rear-shot, and even when this low-voltage _side coil is rear-shot, it can lead to burnout of the receiver or fire. This is an attempt to take countermeasures.

FIG. 1 shows a circuit configuration (not shown) of a deflection device showing one embodiment of the present invention, and a horizontal drive circuit 7.
, a horizontal deflection output circuit 8 , a high voltage circuit 10 , and a rear shot detection/safety circuit 11 . Among these circuits, the circuits other than the rare short detection/safety circuit 11 are known, so the description of these known circuits will be simplified.

The horizontal drive circuit 7 includes a drive transistor 12 and a drive transformer 13, and amplifies the horizontal pulse sent from the horizontal oscillation circuit and sends the voltage pulse, which has undergone waveform shaping, to the horizontal deflection output circuit 8. It is added to.

The horizontal deflection output circuit 8 includes a horizontal output transistor 14 , a damper diode 15 , a resonant capacitor 16 , a horizontal deflection coil 17 , and an S-shaped correction capacitor 18 . Horizontal output transistor 1
4 performs a switching action upon receiving voltage pulses sent from the horizontal drive circuit 7, and applies a sawtooth wave current to the horizontal deflection coil 17 in cooperation with the damper diode 15. On the one hand, the resonant capacitor 16 and the horizontal deflection coil 17 generate flyback pulses by their resonant action, which are applied to the high voltage circuit 10.

The high voltage circuit 10 includes a flyback transformer 20,
A high voltage rectifier diode 21, a capacitor 22,
It consists of an input power source 24. The high voltage side terminal of the low voltage side coil (primary coil) 23 of the flyback transformer 20 is connected to the common terminal of the horizontal deflection coil 17 and the resonant capacitor 16, and the low voltage side terminal of the low voltage side coil 23 is connected to the input power source 24. It is connected to the. On the other hand, flyback transformer 20
A high voltage side terminal of a high voltage side coil (secondary coil) 25 is connected to an anode 27 of a CRT cathode ray tube 26 via the high voltage rectifier diode 21.
In this configuration, the high voltage circuit 10 boosts the flyback pulse applied from the horizontal deflection output circuit 8 using the flyback transformer 20, further rectifies the signal using the high voltage rectifier diode 21, and sends the rectified output to the anode 27. It is added to.

The reduction detection/safety circuit 11 reliably detects reduction occurring in the high voltage side coil 25 of the flyback transformer 20, and is a characteristic circuit of this embodiment. This rare short detection/safety circuit 11 is a rare short detection circuit 28.
, a gate circuit 30 , and a fuse circuit 31 .

The rarest detection circuit 28 includes a resistor 38.
, a detection transformer 32, a diode 33 as a rectifier circuit, and a capacitor 34 as a smoothing circuit.
and distribution resistors 35 and 36 for voltage division,
One end side of the primary coil 37 of the detection transformer 32 is connected to the input power supply 24, and the primary coil 37
The other end is at a reference potential (ground potential in this example)
It is connected to the. And this primary coil 3
A resistor 38 is connected in parallel to 7. On the other hand, one end of the secondary coil 40 of the detection transformer 32 is connected to a reference potential (earth potential in this embodiment), and the other end of the coil 40 is connected to the anode of the diode 33. The cathode of this diode 33 is connected to a capacitor 34 and one end of a distribution resistor 35, and the other end of the distribution resistor 35 is connected to one end of a distribution resistor 36 and the gate of a thyristor 43 as a gate circuit. has been done. Then, the cathode side of the thyristor 43 and the capacitor 34 and the resistor 36
The other end side of each is connected to the reference potential side (ground potential in this embodiment). The distribution resistor 3
5 and 36 divide the DC voltage generated in the capacitor 34 and apply it to the gate of the thyristor 43.

On the other hand, the anode of the thyristor 43 is connected to the fuse circuit 31. This fuse circuit 31
is a DC power supply 44 that functions as a fuse blowing power supply.
, a fuse 45, and a resistor 46.The anode of the thyristor 43 is connected to the DC power supply 44 via the fuse 45, and the anode is connected to the primary drive transformer 13 via the resistor 46. Connected to side coil terminal A.

In this embodiment configured as described above, when the circuit is in operation, the low voltage side coil 23 of the flyback transformer 20 receives a DC component current I _BDC and a deflection period as shown in FIG. An alternating current component current i _B having one cycle of T _H is flowing. this current
i _B is the low voltage side coil 2 of the flyback transformer 20
3 or the high-voltage side coil 25, the alternating current increases, but under normal conditions when no shortfall occurs, the alternating current remains constant with no increase or decrease. As these DC component and AC component currents flow, e ₁ = (I _BDC + i _B ) at both ends of the primary coil 37.
A voltage of R ₁ is generated. However, R ₁ is resistor 38
is the resistance value of In other words, e ₁ is the DC component voltage
It is a combination of R ₁ ×I _BDC and the AC component voltage R ₁ ×i _B , of which only the AC component voltage is separated by the detection transformer 32 and sent to the secondary coil 40 in a boosted state. It is taken out as voltage e ₂ . That is, it is expressed as a voltage of e ₂ =R ₁ ×i _B ×n. However, n is the secondary coil 40 and the primary coil 37.
is the turns ratio.

This voltage e ₂ is half-wave rectified by a diode 33 and further smoothed by a capacitor 34. As a result, e ₂ is present at both ends of the capacitor 34.
In other words, a DC voltage _e3 proportional to the peak-to-peak current value _IBM of the AC current _iB flowing through the primary coil 37 is generated. This DC voltage e ₃
is divided by the distribution resistors 35 and 36, and the resistance value of the resistor 35 is R ₂ and the resistance value of the resistor 36 is R ₃
Then, a voltage of e ₄ =e ₂ ×R ₃ /(R ₂ +R ₃ ) will be applied to the gate of the thyristor 43.

The thyristor 43 opens its gate when the voltage on the gate side becomes larger than a predetermined voltage reference value. Therefore, as mentioned above, if a rare short occurs in the flyback transformer 20,
As I _BM increases, the DC voltage e ₄ applied to the gate also increases correspondingly, and this e ₄ exceeds the voltage reference value of the thyristor 43. As a result, the gate of the thyristor 43 is opened, and a large amount of fusing current flows directly from the DC power supply 44 to the fuse 45.
The fuse 45 is blown, and the voltage applied from the DC power supply 44 to the primary coil end A of the drive transformer 13 through the resistor 46 is cut off. In other words,
As a result of cutting off the drive voltage applied to the low voltage side coil 23 of the flyback transformer 20, it is possible to prevent dangers such as fires caused by the rare short.

By changing the resistance values R ₂ and R ₃ , the distribution ratio of e ₃ can be changed depending on the voltage. The time point at which the abnormality is determined can be set arbitrarily.

As described above, according to this embodiment, there is no need to interpose the detection coil 5 between the low voltage side coil 23 and the high voltage side coil 25 of the flyback transformer 20, as in the conventional example. The magnetic coupling between the two coils 23 and 25 is not deteriorated, and the necessary minimum appropriate insulation distance can be ensured between the two coils 23 and 25, and furthermore, it is possible to reliably prevent dangers due to shortcuts.

In the above embodiment, a circuit configuration is shown in which the high voltage output and the horizontal deflection output are not separated, but in the case of separating the high voltage output and the horizontal deflection output, the horizontal deflection coil 17 and the S-shaped correction capacitor 18 become unnecessary. However, even in this case, only the horizontal deflection coil 17 can be replaced with a dummy inductance.

Further, the present invention is not limited to the circuit configuration shown in FIG. 1, and various circuit changes are possible.
For example, in the above embodiment, the primary coil 37 of the detection transformer 32 is provided with a resistor 38, but this may be omitted. In this case, the primary coil 37
A voltage of e ₁ '=L×di _B /dt is generated (L is the inductance of the coil 37), and the alternating current changing component of i _B can be detected.

Further, in this embodiment, the AC voltage e ₂ taken out to the secondary coil 40 is half-wave rectified by the diode 33, but it may be full-wave rectified.
Furthermore, in the circuit shown in FIG. 1, the fuse 45 is connected to the horizontal drive circuit 7 and the horizontal deflection output circuit 8.
Although the fuse 45 is indirectly connected to the low voltage side coil 23 through the
It may also be connected directly to Furthermore, in the circuit shown in FIG. 1, the AC component of the low voltage side coil 23 is extracted using the detection transformer 32, but in this way,
By using the detection transformer 32, the entire circuit can be combined with the detection transformer 32 and the flyback transformer 2.
0 to the cold side, which is the primary side of the transformers 20 and 32, and the hot side, which is the secondary side of the transformer.
You get the benefit of AC isolation.

Of course, it is also possible to extract the AC component of the low voltage side coil 23 without using the detection transformer 32. In this case, for example, as shown in FIG. Bye. Furthermore, in this embodiment, the thyristor 43 is used as the gate circuit, but it goes without saying that this may be constructed from other circuit elements such as transistors.

〔Effect of the invention〕

As explained above, the present invention can be configured without interposing any circuit element such as a coil between the low-voltage side coil and the high-voltage side coil of the flyback transformer, so that the electromagnetic coupling between the two coils is not deteriorated. In addition, the necessary minimum appropriate insulation distance can be secured between both coils. Furthermore, since the present invention detects the current flowing through the low-voltage side coil of the flyback transformer to detect a shortfall, it is of course possible to detect a shortfall in the high-voltage side coil of the flyback transformer. Even if a rare substance occurs, it can be detected reliably, and safety against the occurrence of a rare substance is completely ensured.

Furthermore, when the occurrence of a rare short is detected by the rare short detection circuit, the gate of the gate circuit is opened and the fusing current flows directly from the fuse blowing power supply, so the fuse blows instantly, ensuring reliable operation. The quality will be much higher.

In addition, since the configuration is configured to detect the rarest by detecting the current in the low-voltage side coil of the flyback transformer, there is no need to separately draw out the wiring for detecting the rarest from the flyback transformer, thereby reducing the complexity of wiring. , it is possible to facilitate wiring work and reduce device costs. In addition, since the configuration is such that the current of the low voltage side coil of the flyback transformer is detected to detect the rare short, it is possible to detect the rare short regardless of the output side circuit specifications of the high voltage side coil, and its practical value is also great. It is.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention;
FIG. 2 is a circuit diagram of a main part of another embodiment of the present invention, and FIG.
The figure shows the waveforms of the AC component voltage and current flowing through the low-voltage side coil of the flyback transformer during the deflection period, Figure 4 shows the equivalent circuit of the deflection circuit when a rarest occurs, and Figure 6 shows the conventional rarest detecting means. FIG. 6 is a circuit diagram of the high voltage generating circuit, and is a sectional view showing the detailed structure of the winding portion of the flyback transformer shown in FIG. 1...Flyback transformer, 2...High voltage side coil, 3...Low voltage side coil, 4, 5...Detection coil, 6
...Horizontal oscillation circuit, 7...Horizontal drive circuit, 8...Horizontal deflection circuit, 10...High voltage circuit, 11...Rear short detection/safety circuit, 12...Drive transistor, 13...Drive transformer, 14...Horizontal output transistor, 15...Damper diode , 16...
Resonant capacitor, 17...Horizontal deflection coil, 18...
S-shaped correction capacitor, 20... Flyback transformer, 21... High voltage rectifier diode, 22... Capacitor, 23... Low voltage side coil, 24... Input power supply, 25
...High voltage side coil, 26...CRT cathode ray tube, 27
...Anode, 28... Rare short detection circuit, 30
...Gate circuit, 31...Fuse circuit, 32...Detection transformer, 33...Diode, 34...Capacitor, 35, 36...Distribution resistor, 38, 41, 4
2, 46...Resistor, 37...Primary side coil, 40...
Secondary coil, 43...thyristor, 44...DC power supply, 45...fuse, 50...capacitor.

Claims (1)

[Scope of Claims] 1. A deflection device including: a horizontal drive circuit for horizontal scanning driving of a cathode ray tube; and a flyback transformer for boosting the output of the horizontal drive circuit and applying the output power to the anode of the cathode ray tube; A fuse connected directly or indirectly to the low voltage side coil of the flyback transformer; A fuse blowing power supply that supplies a blowing current to the fuse; A fuse blowing power supply that detects the alternating current component flowing through the low voltage side coil of the flyback transformer, and a rare short detection circuit that outputs a DC voltage corresponding to the magnitude of the current value; when the output voltage of the rare short detection circuit exceeds a reference value, a gate is opened to flow a blowing current directly from the fuse blowing power source to blow the fuse; A deflection device comprising: a gate circuit which blows out and prevents voltage application to the low voltage side coil of the flyback transformer. 2. The ratio detection circuit consists of a detection transformer with a primary coil connected to one end of the low-voltage side coil of the flyback transformer, a rectifier circuit connected to one end of the secondary coil of this detection transformer, and an output voltage of this rectifier circuit. 2. The deflection device according to claim 1, further comprising a smoothing circuit for smoothing the DC output voltage of the smoothing circuit, and a distribution resistor for dividing the DC output voltage of the smoothing circuit. 3. The gate circuit comprises a thyristor, the cathode of the thyristor is connected to the reference potential side, the anode is connected to the fuse side, and the gate is connected to the output side of the rare short detection circuit. The deflection device according to item 1 or 2. 4. The deflection device according to claim 2, wherein the rectifier circuit is constituted by a diode, and the smoothing circuit is constituted by a capacitor. 5. The deflection device according to claim 2, wherein a resistor is connected in parallel to the primary coil of the detection transformer.