JPH0586111B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a deflection device for a television receiver, etc., and particularly to a deflection device for a television receiver, etc. This invention relates to a deflection device comprising means for preventing the above.

[Conventional technology]

Figure 3 shows a television receiver and a general CRT.
A typical basic circuit of a deflection device used in a display device is shown.

This basic circuit has a horizontal deflection output circuit 1 and a high voltage circuit 2. The horizontal deflection output circuit 1
is a horizontal output transistor 3, a damper diode 4, a resonant capacitor 5, and a horizontal deflection coil 6.
and an S-shaped correction capacitor 7. The horizontal output transistor 3 performs a switching action in response to voltage pulses sent from a horizontal drive circuit (not shown), and applies a sawtooth wave current to the horizontal deflection coil 6 in cooperation with the damper diode 4. On the one hand, the resonant capacitor 5 and the horizontal deflection coil 6 generate flyback pulses by their resonant action, which are applied to the high voltage circuit 2.

The high voltage circuit 2 consists of a flyback transformer 8 and a high voltage rectifier diode 10. One side terminal of the low voltage coil (primary coil) 12 of the flyback transformer 8 is connected to the cathode of the damper diode 4,
It is connected to a common terminal of the horizontal deflection coil 6 and the resonant capacitor 5, and the other end terminal of the low voltage coil 12 is connected to an input power source 13. On the other hand, the high voltage side terminal of the high voltage coil (secondary coil) 14 of the flyback transformer 8 is connected to the anode 16 of the cathode ray tube 15 via the high voltage rectifier diode 10.
It is connected to the. In this configuration, the high voltage circuit 2 uses the flyback transformer 8 to step up the flyback pulse applied from the horizontal deflection output circuit 1, rectifies the signal using the high voltage rectifier diode 10, and outputs the rectified output _EH . It is added to the anode 16.

[Problem that the invention seeks to solve]

When operating a deflection device having the basic circuit described above, if an error occurs during circuit design or manufacturing, abnormalities such as rare shorts may occur in the high voltage coil 14 of the flyback transformer 8, which may cause disasters such as fire. . The circuit design mistakes include the core 11 of the flyback transformer 8 and the high voltage coil 14.
Possible causes include abnormal heat generation, or poor withstand voltage between the coils 12 and 14 or between the coil stacks. Further, as a manufacturing error, it is possible that a rear shot occurs due to a mistake during the winding work of the coils 12 and 14, or an internal discharge occurs due to a mistake in insulation processing of the coils 12 and 14.

Although the design and manufacturing of the deflection device is controlled to prevent the above-mentioned mistakes from occurring, it is difficult to completely eliminate such mistakes even if sufficient care is taken. Therefore, for example, a temperature fuse connected in series to the low voltage coil 12 or the input power supply 13 is disposed in the flyback transformer 8,
When the flyback transformer generates abnormal heat due to the above-mentioned mistake, the abnormal high-temperature heat generation is used to blow out the fuse and prevent the application of voltage to the flyback transformer 8, thereby preventing the occurrence of the above-mentioned disaster. is possible.

However, when arranging the above-mentioned temperature fuse, there is an extremely large potential difference between the temperature fuse and the high voltage coil 14, so if the temperature fuse is placed close to the coil 14, there is a problem that discharge will occur between the two. However, insulation treatment to avoid such discharge is extremely difficult. Also, in order to prevent the discharge, it is possible to separate the temperature fuse from the high voltage coil 14, but in that case,
This is disadvantageous in that the temperature of abnormal heat generated by the rear end of the high voltage coil 14 is difficult to be transmitted to the temperature fuse, delaying safety operation (fuse blowing operation), and making it impossible to prevent fires and the like. Furthermore, the drive frequency of the flyback transformer 8 is generally
Since it is high at 15.75KHz to 130KHz, low voltage coil 12
It is necessary to increase the degree of electromagnetic coupling between the high-voltage coil 14 and the high-voltage coil 14, but as mentioned above, it is necessary to install a large-sized one such as a temperature fuse inside the flyback transformer (for example, between the coils 12 and 14). Then,
There is also the problem that the degree of electromagnetic coupling is reduced and the basic performance of the flyback transformer 8 is impaired.

The present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to provide a means for quickly and reliably detecting abnormalities caused by the rare shorts of flyback transformers and preventing disasters from occurring. Moreover, by taking such measures, it is an object of the present invention to provide a deflection device that has almost no adverse effect on the basic performance of a flyback transformer.

[Means for solving problems]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention includes a horizontal deflection output circuit that receives an output signal from a horizontal drive circuit and generates a flyback pulse; boosts the flyback pulse from the horizontal deflection output circuit and supplies the output power to the anode side of the cathode ray tube. a protective fuse connected directly or indirectly to a low-voltage coil of the flyback transformer;
a primary current detection circuit that detects a current flowing through a low voltage coil of the flyback transformer; a secondary current detection circuit that detects a high voltage current flowing through a high voltage coil of the flyback transformer; a detected value comparison circuit that outputs an operation signal when the current capacity detected by the secondary side current detection circuit becomes larger than the reference capacity of the current detected by the secondary side current detection circuit; and an operation signal from the detected value comparison circuit. and a gate circuit that opens the gate to flow a fusing current and blow out the protective fuse to prevent voltage application to the low voltage coil of the flyback transformer. There is.

[Effect]

In the present invention configured as above,
Under normal conditions when there is no abnormality in the flyback transformer, the current capacity detected by the primary side current detection circuit is less than the reference capacity of the current detected by the secondary side current detection circuit. Therefore, the gate of the gate circuit is closed and no blowing current flows through the protective fuse.

On the other hand, if an abnormality such as a reduction occurs in the high-voltage coil of the flyback transformer, the current flowing through the low-voltage coil increases rapidly. As a result, the current capacity detected by the primary-side current detection circuit changes to the current detected by the secondary-side current detection circuit (this current hardly increases even if the high-voltage coil is short-circuited). becomes larger than the reference capacitance of , an operation signal is applied from the detection value comparison circuit to the gate circuit, and the gate of the gate circuit is opened. By opening the gate, a large amount of blowing current flows through the protective fuse, causing the fuse to blow. By blowing the fuse, application of voltage to the low voltage coil is blocked. The operation of the flyback transformer is stopped, and the occurrence of a fire or the like due to abnormal heat generation of the flyback transformer is prevented.

〔Example〕

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

FIG. 1 shows a circuit configuration of a deflection device showing one embodiment of the present invention. In the figure, the deflection device includes a horizontal oscillation circuit (not shown), a horizontal drive circuit 17, a horizontal deflection output circuit 1, and a high voltage circuit 2.
and an abnormality detection/safety protection circuit 18. Among these circuits, the circuits other than the abnormality detection/safety protection circuit 18 are well known, so the description of those well-known circuits will be simplified.

The horizontal drive circuit 17 has a drive transistor 20 and a drive transformer 21, and amplifies the horizontal pulse sent from the horizontal oscillation circuit and sends the voltage pulse, which has been waveform-shaped, to the horizontal deflection output circuit 1. It is added to.

The horizontal deflection output circuit 1 is constructed in the same manner as in the case of FIG.
This is added to the high voltage circuit 2.

The high voltage circuit 2 consists of a flyback transformer 8 and a high voltage rectifier diode 10, and as in the case of FIG. 3, the flyback pulse applied from the horizontal deflection output circuit 1 is boosted by the flyback transformer 8, and further Signal rectification is performed by the high voltage rectifier diode 10, and the rectified output is transferred to the anode 1.
Add to 6.

The abnormality detection/safety protection circuit 18 reliably detects abnormalities such as short circuit occurring in the high voltage coil 14 of the flyback transformer 8, and is a characteristic circuit of this embodiment. The abnormality detection/safety protection circuit 18 includes a primary current detection circuit 19, a secondary current detection circuit 23, a gate circuit 24, a protection fuse 25, and a detected value comparison circuit 26.

The primary side current detection circuit 19 includes a low voltage coil 1
An AC path capacitor 27 that removes an AC component of the current I _B flowing through the current I B and a first detection resistor 28 that converts the DC component of the current I _B from which the AC component has been removed into a voltage and detects it in parallel. One end of the primary current detection circuit (parallel circuit) 19 is connected to the low voltage side (winding start side) of the low voltage coil 12, and the other end of the circuit 19 is connected to the input power supply via a protective fuse 25. 13, and the negative side of the input power source 13 is connected to the reference potential side (earth side in the figure).

The secondary current detection circuit 23 is connected to the high voltage coil 1
4, an AC path capacitor 31 that removes the AC component of _the high voltage current _IH , a capacitor 40 that removes noise, and a bias power supply 32. . The second detection resistor 30 and the capacitor 40 form a parallel circuit, and one end of this parallel circuit is connected to a common connection between the primary current detection circuit 19 and the protection fuse 25 via the bias power supply 32. The other end of the parallel circuit is connected to the low voltage side (winding start side) of the high voltage coil 14 via a resistor 33. One end of the AC pass capacitor 31 is connected to a common connection between the resistor 33 and the low voltage side of the high voltage coil 14, and the other end is connected to the ground side.

Further, in this embodiment, the detected value comparison circuit 26 is constituted by a transistor 34, and the gate circuit 24 is constituted by a thyristor 35. The base side of the transistor 34 is the resistance voltage side of the low voltage coil 12, that is, the primary side current detection circuit 1.
The transistor 3 is connected to one end side of the transistor 9.
The emitter side of 4 is one end side of the secondary current detection circuit 23, that is, the second detection resistor 30 and the resistor 3
The collector side of the common connection with the thyristor 3 is connected to the gate side of the thyristor 35 via a resistor 36, respectively.

Furthermore, on the gate side of the thyristor 35, a resistor 37 and a capacitor 38 for noise removal are further provided.
The other end of the parallel circuit is connected to the cathode side of the thyristor 35, and the connection between these parallel circuits and the cathode side is further connected to the reference potential side (earth side in the figure). .

On the other hand, the anode side of the thyristor 35 is the other end side of the primary current detection circuit 19, that is, the detection circuit 1
9 and the protective fuse 25.

In addition, the low voltage side of the high voltage coil 14 is connected to the ground via the AC path capacitor 31, that is, the cathode of the thyristor 35, the resistor 37, and the capacitor 38.
The connection between the low voltage side of the coil 14 and the capacitor 31 is connected to the common connection side of the coil 14.
Familiar with ABL (Automatic Brightness Limiter).

In the figure, numeral 41 indicates a flyback transformer unit, and P ₁ to _{P 5} indicate terminals of the unit.

In this embodiment configured as described above, when the brightness of the cathode ray tube 15 is increased while the circuit is being driven, the high voltage output current I _H applied to the anode 16 of the cathode ray tube 15 increases. On the other hand, if this high voltage output current I _H increases, the current I _B flowing from the input power supply 13 to the low voltage coil 12 also increases. this current
I _B includes an AC component and a DC component, and the relationship between the DC component current I _BDC and the high voltage output current I _H is the second
As shown in the figure. According to this figure, the current I _BDC is
A variable DC component i _B that increases in proportion to the increase in the high voltage output current I _H is added to the constant DC component I _BDCO , and when I _H changes from 0 to the maximum value I _HM of the operating range. , I _BDC changes by ΔI _BDC . this
The actual current of I _BDC includes a large sawtooth wave component, but in Figure 2, even the average current value of I _BDC
represents.

As mentioned above, when the brightness of the cathode ray tube 15 changes, the current I B is applied to the low voltage coil 12, and the current I _B is applied to the high voltage coil 1.
A high voltage current _IH flows through each of the terminals 4 and 4. Then, the DC component current I _BDC of the current I _B flowing through the low voltage coil 12
is detected by the primary side current detection circuit 19 as follows. That is, as a result of the AC component current of I _B being removed by the AC path capacitor 27, the current at both ends of the capacitor 27 is completely smoothed.
I A voltage proportional to _BDC appears. In other words, the product of the DC component current I _BDC and the resistance value R ₁ of the first detection resistor 28, that is, the voltage e _B = R ₁ × I _BDC appears, and the DC component current capacity I _BDC indirectly increases. It is converted into a voltage value e _B and detected. This detected value e _B is applied to the base of the transistor 34 using the Q point of the circuit shown in FIG. 1 as a reference point.

On the other hand, the high voltage current _IH flowing through the high voltage coil 14 is detected by the secondary current detection circuit 23 as follows. That is, when the high voltage current I _H flows through the second detection resistor 30 to the high voltage coil 14, if the resistance value of the second detection resistor 30 is _R2 , then e _H = A ripple-free DC voltage of I _H ×R ₂ appears. This means that the high voltage current I _H is indirectly converted into a voltage e _H and detected. Then, with the Q point as the reference point, bias power supply 3
The output voltage of the secondary current detection circuit 23, which is the sum of the detected value _eH and the voltage E _S of the second embodiment, is applied to the emitter of the transistor 34.

This bias power supply 32 is connected to both detection circuits 19 and 23.
It is equipped to balance the detection current capacity.

In other words, when point Q is the reference point, low voltage coil 1
As mentioned above, the negative DC component I _BDC flowing in the low voltage coil 12 (when viewed from point Q as a reference point, the current flowing in the low voltage coil 12 is a negative current) is the sum of the constant component I _BDCO and the variable component i _B In order to balance this constant component I _BDCO , a negative voltage corresponding to this I _BDCO is applied from the bias power supply 32 to the second detection resistor 30. As a result, the balanced relationship between e _B and e _H is replaced by the relationship between the DC changing component i _B flowing through the low voltage coil 12 and the high voltage current I _H flowing through the high voltage coil 14 .

The transistor 34 operates normally when the high-voltage coil 14 does not have a rearrangement, that is, (E _S +e _H )≧e _B
It remains off when . On the other hand, when a short circuit occurs in the high-voltage coil 14, the changing component i _B of the DC current flowing in the low-voltage coil 12 becomes nearly twice as large as normal, resulting in a state where (E _S +e _H )<e _B. That is, when a rare short occurs in the high voltage coil 14, the current flowing in the low voltage coil 12 increases significantly. On the other hand, on the high-voltage coil 14 side, a large current circulates around the local closed circuit part created by the coil short, but the current flowing through the entire high-voltage coil 14 hardly changes due to the occurrence of the rare short (of course When the rare short circuit is short-circuited to the ground side, a large current flows through the high-voltage coil, but normally even if a rare short circuit occurs, this rare short part will not be short-circuited to the ground). As a result, in this embodiment (the present invention), the detected current of the high voltage coil 14, which hardly changes depending on the high voltage coil's rear shot, is used as the reference value, and this reference value is used as the detected value of the primary side (low voltage coil side) current. By comparison, we are detecting the occurrence of rares. The transistor 34 turns on when (E _S +e _H )<e _B and applies an operating signal (collector voltage) to the gate of the thyristor 35 . In this case, since the collector voltage becomes quite large, it is not desirable to apply that voltage to the thyristor 35 as it is. Therefore, in the circuit shown in Figure 1,
The collector voltage is divided by resistors 36 and 37, and when the transistor 34 is turned on, an operation signal is applied to the gate of the thyristor 35, the voltage being higher than the reference voltage on the cathode side of the thyristor 35.

When this operation signal is input, the thyristor 35 opens its gate, causes a blowing current to flow through the protective fuse 25, and blows out the fuse 25. In this way, in the circuit of this embodiment, the detection resistor 2
8, 30 resistance values R ₁ , R ₂ and bias power supply 32
The operation of the transistor 34, that is, the operating point of the thyristor 35, is determined depending on how the voltage _ES is determined.

The process of determining R ₁ and R _{2 ES} can be expressed using the following formula.

First, the DC component I _BDC flowing through the low voltage coil 12
is expressed as I _BDC = AI _H + I _BDCO (1) (where A is a constant).

Furthermore, e _H and e _B are also expressed as Q reference points in FIG. 1 as follows.

-e _H = I _H ×R ₂ ...(2) -e _B = I _BDC ×R ₁ ...(3) Substituting equation (1) into equation (3), -e _B = A × I _H × R ₁ +I _BDCO ×R ₁ In normal operation without a reduction in the flyback transformer, the condition for balancing the current capacity of the DC component current I _BDC flowing in the low voltage coil 12 and the current capacity of the current I _H flowing in the high voltage coil 14 is e _B =
Since E _S +e _H , I _H ×R ₂ + E _S = A × I _H × R ₁ + I _BDCO × R ₁ , so I _H × R ₂ = A × I _H × R ₁ ∴R ₂ = A × R ₁ E _S =I _BDCO × R ₁ In other words, R ₁ , R ₂ , and E _S are the circuit constants to be determined. Now, if E _S is determined first, R ₁ and R ₂ are R ₁
= E _S /I _BDCO , R ₂ = A x E _S /I _BDCO .

In this embodiment, if the value of E _S is set appropriately large with a margin in consideration of circuit variations, the thyristor 35 will always maintain an off state during normal operation, and the gate will not be opened. do not have.

On the other hand, if an abnormality such as rare short occurs in the high voltage coil 14 of the flyback transformer 8,
As mentioned above, there is almost no change in the current flowing through the high voltage coil 14, whereas the current flowing through the low voltage coil 12
The change component i _B of the current flowing through the current increases rapidly, and especially in the case of an abnormality that causes the flyback transformer 8 to ignite, the increase in i _B will be nearly twice as much as ΔI _BDC in Fig. 2. . As a result, e _B > (e _H + E _S ),
The transistor 34 operates sufficiently before the ignition occurs, the thyristor 31 is turned on, and the gate is opened. Since the protection fuse 25 is immediately blown by opening the gate, the operation of the flyback transformer 8 is stopped, and the occurrence of a fire or the like due to the short circuit of the flyback transformer 8 is prevented.

In the above embodiment, the circuits for detecting the short circuit and ensuring its safety, that is, the circuits such as the primary and secondary current detection circuits 19 and 23, the gate circuit 24, and the detected value comparison circuit 26, are transformers. It is formed compactly within the unit 41, and the desired purpose can be achieved without introducing any operating signals from outside the unit 41. Therefore, there is no need to increase the number of terminals of the transformer unit 41, and the above purpose can be achieved simply by adding a circuit within the conventional transformer unit, which simplifies manufacturing and assembly of the device, and also makes handling easier. It is also extremely convenient.

In the above embodiment, a circuit configuration is shown in which the high voltage circuit and the horizontal deflection output circuit are not separated, but if they are separated, the horizontal deflection coil 6 and the S-shaped correction capacitor 7 become unnecessary. However, even in this case, only the horizontal deflection coil 6 can be used as 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 bias power supply 32 is provided on the side of the secondary current detection circuit 23 to balance the constant DC component I _BDCO of the current flowing through the low voltage coil 12. The bias power supply that adds DC voltage is connected to the primary current detection circuit 1.
9 to cancel out the negative DC current component _IBDCO .

Further, in the circuit shown in FIG. 1, the high-voltage coil 14 is not wound in segments, but it may be wound in multiple parts to form a multi-singular type. In this case, diodes are connected in series between each divided coil.

Further, in this embodiment, capacitors 38 and 40 for removing noise are provided, but these may be omitted.

Further, in this embodiment, the thyristor 35 is used as the gate circuit, but this may be configured with other circuit elements such as a transistor. Further, in the embodiment described above, the detected value comparison circuit is formed of the transistor 34, but it may be formed of a thyristor, a differential amplifier, or the like.

〔Effect of the invention〕

Since the present invention is configured as explained above, it is possible to quickly and reliably detect an abnormality caused by a rare shoot or the like in a flyback transformer, and take safety measures to prevent the abnormality caused by the abnormality of the flyback transformer. It is possible to prevent disasters such as fires from occurring.

In addition, it is not necessary to install a temperature fuse inside the flyback transformer to detect the abnormality, so the basic performance of the flyback transformer is not impaired.Furthermore, the circuit configuration is simple, so it is easy to use technology. This makes it possible to provide a deflection device that is extremely superior both in terms of both commercial and economical aspects. Furthermore, in the present invention, we have focused on the fact that even if a short circuit occurs in the high-voltage coil of a flyback transformer, the current flowing through the high-voltage coil hardly changes. Since it functions as a reference capacity (reference value) for comparison with the current capacity detected by the detection circuit, there is no need to separately prepare a dedicated reference power supply for comparison with the primary side current detection capacity. This makes it possible to simplify the circuit configuration and reduce the cost and size of the device.

Furthermore, the present invention detects the current flowing through the low-voltage coil of the flyback transformer and compares it with the reference current capacity to detect the reduction of the flyback transformer. In case,
This rare short can be reliably detected by detecting a rapid change in the current of the low voltage coil, and the safety reliability for the rare short will be much higher.

[Brief explanation of the drawing]

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 characteristic diagram showing the relationship between the DC component current I _BDC flowing through the low-voltage coil and the high-voltage current I _H flowing through the high-voltage coil, and FIG. 3 is a general basic circuit diagram of a deflection device. 1...Horizontal deflection output circuit, 2...High voltage circuit, 3...Horizontal output transistor, 4...Damper diode,
5... Resonance capacitor, 6... Horizontal deflection coil, 7...
S-shaped correction capacitor, 8... flyback transformer, 10... high voltage rectifier diode, 11... core, 1
2...Low voltage coil, 13...Input power supply, 14...High voltage coil, 15...Cathode ray tube, 16...Anode, 17
...Horizontal drive circuit, 18...Abnormality detection/safety protection circuit, 19...Primary side current detection circuit, 20...Drive transistor, 21...Drive transformer, 23
...Secondary side current detection circuit, 24...Gate circuit, 25
...protection fuse, 26...detected value comparison circuit, 27...
AC path capacitor, 28...first detection resistor,
30... Second detection resistor, 31... AC path capacitor, 32... Bias power supply, 33... Resistor, 34
...transistor, 35...thyristor, 36...resistor, 37...resistor, 38...capacitor, 40...capacitor, 41...transformer unit.

Claims (1)

[Claims] 1. A horizontal deflection output circuit that receives an output signal from a horizontal drive circuit and generates a flyback pulse; boosts the flyback pulse from this horizontal deflection output circuit and supplies the output power to the anode side of the cathode ray tube. a flyback transformer added to the deflection device; a protective fuse connected directly or indirectly to the low voltage coil of the flyback transformer; a primary current for detecting the current flowing through the low voltage coil of the flyback transformer; a detection circuit; a secondary current detection circuit that detects a high voltage current flowing through the high voltage coil of the flyback transformer;
a detected value comparison circuit that outputs an operation signal when the current capacity detected by the primary side current detection circuit becomes larger than the reference capacity of the current detected by the secondary side current detection circuit; a gate circuit that opens the gate to flow a fusing current when receiving an operating signal from the detected value comparison circuit, blows out the protective fuse, and blocks application of voltage to the low-voltage coil of the flyback transformer; A deflection device characterized by: 2. The detected value comparison circuit is composed of transistors, and the primary-side current detection circuit and secondary-side current detection circuit each include a capacitor that removes the AC component of the detected current, and a DC detection circuit obtained by this capacitor. The gate circuit is composed of a thyristor, and the base side of the transistor is connected to a primary-side current detection circuit, and the circuit receives the primary-side detection current. A corresponding voltage is applied, the emitter side of the transistor is connected to a secondary current detection circuit, and a voltage corresponding to the detected current on the secondary side is applied from the same circuit, and the collector side of the transistor is connected to a secondary current detection circuit. The thyristor is connected to the gate side via a resistor, the cathode side of the thyristor is connected to a reference potential side, and the anode side of the thyristor is connected to one end side of a protective fuse. A deflection device according to scope 1. 3. The device according to claim 1 or 2, characterized in that one side of the primary current detection circuit and the secondary current detection circuit is equipped with a bias power supply for applying a bias current. Deflection device.