JPS63272281A - High voltage generator - Google Patents

Abstract

PURPOSE:To improve safety by detecting a fault such as a short-circuit in a flyback transformer depending on the change in the primary DC input current if the fault takes place and the temperature rises abnormally so as to stop the high voltage generation permanently. CONSTITUTION:If a short-circuit takes place in the flyback transformer 1 and lots of energy loss is caused at the short-circuit part, the primary DC input current IB is increased rapidly due to the energy loss and a large negative voltage eB is generated across a 1st sensing resistor 21. Thus, a transistor 28 (TR) is cut off and other TR 29 is conductive. Thus, a thyristor 33 is conductive. Then a current flow a flyback power supply 15 flows to ground through a fuse 23 and the thyristor 33 depending on the relation with the resistance of a low voltage coil 4 to blow the fuse 23. Thus, an accident such as a fire is prevented in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high voltage generator used for applying a DC high voltage to a cathode ray tube of a television receiver, a display device, etc., for example.

[Prior art]

Among conventional high voltage generators using a flyback transformer, a high voltage generator using a coaxial multilayer-wound flyback transformer will be described with reference to FIGS. 7 and 8.

First, FIG. 7 shows a coaxial multilayer winding type flyback transformer. In the figure, l indicates a flyback transformer, and the flyback transformer 1 includes a core 2 formed by abutting U-shaped core members, and a core 2 that is inserted into one leg of the core 2. A low-pressure bobbin 3 is provided, a low-voltage coil 4 is section-wound around the outer periphery of the low-pressure bobbin 3, a high-pressure bobbin 5 is provided to fit around the low-pressure bobbin 3, and an interlayer is formed on the outer periphery of the high-pressure bobbin 5. Paper 6, 6. . . . Five high-voltage winding layers 7A, 7 wound in a coaxial multilayer manner through...
A high voltage coil 7 consisting of B, . . . 7E and a high voltage winding layer 7
A, 7B, . . . , 7E are alternately connected in series with a high voltage tie 8 consisting of five high voltage tie holders 8A, 8B, . It is roughly structured.

Further, FIG. 8 shows the entire circuit configuration, and in FIG. 8, the low voltage coil 4 and the high voltage coil 7 are shown in a simplified manner, and "." in the figure indicates the winding start end. And low voltage coil 4
The high voltage side end of is connected to the horizontal deflection circuit 9. The horizontal deflection circuit 9 includes a horizontal output transistor 101 consisting of an NPN transistor, a resonant capacitor 11, a tampon tie auto 12, a horizontal deflection coil 13 of the deflection yoke.
It consists of a figure-8 correction capacitor 14, etc., the collector side of the transistor 10 is connected to the high voltage end side of the low voltage coil 4, and the emitter is grounded. In addition, the low voltage coil 4
The low voltage end of is a flyback voltage f to which DC voltage E8 is applied.
Connected to i15. On the other hand, in the high voltage coil 7, the high voltage winding layer 7A on the lowest voltage side is connected to an ABL circuit (autom
aticbrightness 11m1tter
) or ground, and the highest voltage side is connected to the anode terminal 17A of the cathode ray tube 17 via a high voltage cable 16 from a high voltage diode (8E) for output.

Note that the cathode terminal 17B of the cathode ray tube 17 is grounded.

In the high voltage generator configured in this manner, a basic pulse is applied to the base of the transistor 10 from a horizontal drive circuit (not shown), so that the transistor 10
A collector pulse (flyback pulse) is output from the collector of 0 to the low voltage coil 4. As a result, a high voltage determined by the number of coil turns is induced in each winding layer 7A to 7E of the high voltage coil 7, and these high voltages are added and rectified by the high voltage diode 8, and the high voltage output voltage E,... A DC high voltage with a high voltage output current I I+ is output to the cathode ray tube 17.

(Problem to be solved by Koukyo) However, in the high voltage generator configured as described above, its effective output is as large as several tens of watts, and if it is not designed and manufactured appropriately, it will generate heat and generate heat. There is a risk of an accident occurring due to ignition, etc.

The first cause of these accidents is due to design.
There was abnormal heat generation in the windings of the core 2, low voltage coil 4, high voltage coil 7, etc. of the flyback transformer 1, and secondly, there was a voltage resistance problem between the low voltage coil 4 and the high voltage coil 7, and between each layer of the high voltage coil 7. etc. are possible. On the other hand, as for manufacturing problems, firstly there is a winding short due to a mistake during winding, and secondly there is an internal discharge due to a mistake in insulation processing.

The problem is that these various causes are well controlled and there is almost no possibility of an accident, but if an accident were to occur, it would lead to a major accident such as a fire.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a reliable high voltage generator with improved safety against fire accidents.

[Means for solving problems]

In order to solve the above problems, the present invention provides a low-voltage coil, a high-voltage coil that generates a high-voltage output by inputting a signal to the low-voltage coil, and a flyback provided at the low-voltage side end of the low-voltage coil. a first detection means for detecting a primary DC input current flowing through the low-voltage coil as a voltage eB; and a high-voltage DC output current flowing through the high-voltage coil as a voltage e□; a second detection means connected to the low-voltage side end of the low-voltage coil, and a second detection means connected to the low-voltage side end of the low-voltage coil; eB” in cooperation with the second detection means.
a DC power supply that applies a DC voltage ES having a relationship of e11+ES; a voltage comparison unit that receives the voltages e8, e, +ES and outputs a signal when the primary DC input current increases abnormally; [Embodiment] An embodiment of the present invention is described below with reference to Figs. 1 to 6. This will be explained in detail with reference to. Note that the same components as those in the prior art described above are given the same reference numerals, and their explanations will be omitted.

1 and 2 show a first embodiment of the present invention.

In the figure, reference numeral 21 denotes a first detection resistor as a first detection means provided between the negative terminal of the flyback power supply 15 and the ground, and an AC component bypass capacitor 22 connected in parallel with the resistor 21. is connected. This reduces the primary DC input current flowing through the low voltage coil 4 to 1. If the resistance value of the first detection resistor 21 is R2□, then 6 B = I
BX R21・・・・・・・・・・・・The completely smoothed DC voltage component eB (
The true value is a negative voltage).

Reference numeral 23 indicates a fuse constituting the operation stopping means of the present invention inserted between the positive side terminal of the flyback power supply 15 and the low voltage side end of the low voltage coil 4, and the fuse 23 is connected to a thyristor 33 to be described later. As a result, the current from the flyback power supply 15 flows through the fuse 23 and the thyristor 33.
The structure is such that it melts while flowing to ground through the

24 is a second detection resistor as a second detection means; 25
indicates a constant voltage power supply that applies a negative DC voltage EB, one end of the resistor 24 is connected to the low voltage side of the high voltage coil 7, the other end is connected to the negative terminal of the constant voltage power supply 25, and the low voltage power supply The positive terminal of 25 is connected to the ground, and the whole is connected in series between the high voltage coil 7 and the ground, and an AC component bypass capacitor 26 is connected in parallel to this series connection. Therefore, since the high voltage output current I□ flows from the constant voltage power supply 25 to the high voltage coil 7 via the second detection resistor 24, the resistance value is set to R24.
Then, at both ends, e u = 1 ++
R24・・・・・・・・・・・・(2) A DC voltage component ell (true value is a negative voltage) is generated, and at the connection point with the low voltage side end of the high voltage coil 7, e HL= e ll + E s ・・・=-・
・-(3) A DC voltage is generated.

Further, 27 is a differential amplifier circuit constituting the voltage comparison means,
The differential amplifier circuit 27 includes an NPN type transistor 28 serving as an inverting input terminal, and another NPN transistor 28 serving as a non-inverting input terminal.
It consists of a known circuit including a type transistor 29 and a negative DC power source 30, and is suspended by another DC power source 31. The base of the transistor 28 is connected to the connection point a, and a DC voltage eB is applied to the base of the transistor 28.
The base of 9 is connected to the connection point and DC voltage ellL is applied thereto. Here, the differential amplifier circuit 27 has a DC voltage e applied to its transistor 28 as described later.
When B becomes large, the circuit is cut off, and the collector voltage of the transistor 28 is applied to the latch circuit 32 side as an output signal.

Furthermore, 32 is a latch circuit which together with the fuse 23 constitutes the operation stop means of the present invention, and the latch circuit 32 is composed of a thyristor 33, a voltage dividing resistor 34 for adjusting the constant voltage, and a capacitor 35 for noise removal. The anode of the thyristor 33 is connected to a connection point C between the fuse 23 and the low-voltage coil 4, and its cathode is grounded, and its gate forms a differential amplifier circuit 27 via a Zener diode 36. A voltage dividing resistor 34 and a capacitor 35 are connected in parallel between the gate side and the ground.

Here, the latch circuit 32 is designed to blow out the fuse 23 when a voltage is applied to the gate of the thyristor 33 and it becomes conductive. The Zener diode 36 is used to raise the so-called operating point so that the thyristor 33 becomes conductive when the collector voltage of the transistor 28 exceeds a predetermined Zener voltage.

The structure of this embodiment will be described below, and its operation will be described next.

First, a voltage e is applied to the transistors 28 and 29 of the differential amplifier circuit 27 from the connection point c, respectively. , eut.

is applied, the differential amplifier circuit 27 is balanced,
The conditions for not generating a signal to the latch circuit 32 are as follows:
From the above formulas (1) and (3), eB = e, L = e,
+Es −・−−−−−(4) Is it necessary?

On the other hand, when the brightness of the cathode ray tube 17 is gradually increased from zero, it is known that the relationship between the primary DC input current '1fif, In and the high voltage output current II (as shown in Figure 2) That is, the primary DC input current fR, IB consists of a constant part with a predetermined current value IBo and a proportional part iB that increases in proportion to the high voltage output current II+, and has a predetermined maximum value i□. is increased by a predetermined value Δ■8. Therefore, the primary surface current input current I. and the high voltage output current 1. are calculated as follows (5).
The relationship is shown in the formula.

From this, substituting equation (5) into equation (1), we get, and from the relationship with equations (1) to (4), E s = I noX R21=”= (8) e++
= in XR21=Ill XR24-・= (9
), the resistance value R2 of each detection resistor 21.24 is
,, R24 and the voltage value Es of the constant voltage power supply 25, equation (4) will hold true.

At this time, from equations (9) and (5), we get: If A is a constant, then the resistance value of each detection resistor 21.24 can be determined based on the predetermined maximum value l11m and the predetermined increase value ΔI8. can.

Thus, the constant voltage power supply 25 that satisfies equation (8) and (1
1) If the detection resistor 21°24 that satisfies the formula is determined,
Equation (4) holds true, and no output signal is generated from the differential amplifier circuit 27 to the latch circuit 32, so the thyristor 33 is in a cutoff state. As a result, all of the primary DC input current In flowing through the fuse 23 flows to the low-voltage coil 4 side, generating a high-voltage output under normal conditions as in the prior art.

Now, a short circuit has occurred in flyback transformer 1.
When a large amount of energy is lost at the short circuit, the temperature inside the flyback transformer 1 begins to rise rapidly. At the same time, due to energy loss, the primary surface current input current■
The value of 8 also rises rapidly, and a large negative voltage eQ is generated across the first detection resistor 21.

As a result, this voltage eB is applied to the base of the transistor 28 of the differential amplifier circuit 27, which turns off the transistor 28 and turns on the other transistor 29. Therefore, the collector voltage of the transistor 28 is applied to the latch circuit 32 via the Zener diode 36 as an output voltage.
is applied to the thyristor 33, making the thyristor 33 conductive.

Thus, due to the relationship with the resistance on the low voltage coil 4 side, the current from the flyback power supply 15 flows to the ground via the fuse 23 and thyristor 33, and the fuse 23 is blown by the overcurrent at this time. Therefore, when the temperature inside the flyback transformer 1 rises in this way, the fuse 23 will melt and no flyback pulse will be generated on the low voltage coil 4 side forever, causing the operation to stop and causing a major accident such as a fire. This can be prevented.

Note that the primary plane current input current Ill is the high voltage output radio wave I11
In reality, the flyback transformer l derives various secondary outputs, so it may be said that it only responds to changes in
There are also variations on the picture tube device side. Then, a Zener tie auto 36 is inserted, and when the collector voltage of the transistor 28 exceeds the Zener voltage value, the thyristor 3
By making 3 conductive, a desired play can be provided.

Further, FIGS. 3 to 5 show modifications of this embodiment.

First, in FIG. 3, in place of the flyback power supply 15 in FIG. 1, the first A detection resistor 21 and a capacitor 22 are provided between the diode bridge 42 and the ground, and the primary surface current input current II3 is detected as a voltage eB (the true value is a negative voltage).

In addition, in FIG. 4, a first detection resistor 21 and a capacitor 22 are provided between the emitter of the horizontal output transistor IO of the horizontal deflection circuit 9 and the ground, and the input current 8 is changed to a voltage eB.
(The true value is a positive voltage).

Furthermore, in FIG. 5, a second detection resistor 24 and a capacitor 2 are connected between the cathode terminal 17B of the cathode ray tube 17 and the ground.
6 is provided, and the high voltage output current I I+ is detected as a voltage eH (the true value is a positive voltage).

In addition, in the case of FIGS. 4 and 5, the detected voltage e n +
Although the polarity of e H is positive in its true value, in this case, the configuration of the differential amplifier circuit 27 may be changed accordingly.

Next, FIG. 6 shows a second embodiment of the present invention, in which the same components as in the first embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted.

However, in FIG. 6, reference numeral 51 denotes a horizontal drive circuit provided before the horizontal deflection circuit 9, and the horizontal drive circuit 51 includes a transistor 52. It is configured as a known circuit including a positive pulse output transformer 53 and the like. Reference numeral 54 indicates a DC power supply for suspending the horizontal drive circuit 51 at, for example, 110V, 55 indicates a fuse provided between the DC power supply 54 and the horizontal drive circuit 51, and a connection point d of the horizontal drive circuit 51 of the fuse 55. is connected to the anode of the thyristor 33 constituting the latch circuit 32.

The present embodiment is configured as described above, but when the temperature of the flyback transformer l rises in the same way as the first embodiment,
Thyristor 33 becomes conductive. As a result, the DC power supply 54
An overcurrent flows from the fuse 55 to the ground via the thyristor 33, blows out the fuse 55, and the horizontal drive circuit 5
1, that is, to stop the operation of the flyback transformer l.

In each of the above-described embodiments, the horizontal deflection circuit 9 is provided with the horizontal deflection coil 13 and the eighth-order correction capacitor 14, or the horizontal deflection circuit may be of a type in which these are not provided. Further, although the differential amplifier circuit 27 is illustrated as a specific example of the voltage comparison means, the voltage comparison means may be configured using an operational amplifier. Also, Fuse 23
The connection position of .degree.55 is not limited to the position of the embodiment. Furthermore, the flyback transformer is not limited to the coaxial multilayer winding type, but may of course be applied to a so-called section winding type flyback transformer in which the high voltage coil is wound in sections in the axial direction of the high voltage bobbin.

[Effect of idea]

The high voltage generator according to the present invention is as described in detail above, and when an accident such as a short circuit occurs in the flyback transformer and the temperature rises abnormally, this is detected from the change in the primary DC input radio wave. However, since the high voltage generation operation is permanently stopped by the operation stop means, the circuit operation is stopped before a major accident such as a fire occurs, and safety can be significantly improved.

[Brief explanation of the drawing]

1 and 2 relate to a first embodiment of the present invention, FIG. 1 is a circuit configuration diagram showing a high voltage generator according to this embodiment, and FIG. 2 is a high voltage output current and a primary DC input current. FIG. 3 is a main circuit configuration diagram showing a modification of the arrangement position of the first detection resistor, and FIG. 4 shows another arrangement position of the first detection resistor. FIG. 7 is a circuit configuration diagram of main parts showing a modification of the arrangement position. FIG. 5 is a main circuit configuration diagram showing a modification of the arrangement position of the second detection resistor, FIG. 6 is a circuit configuration diagram showing a high voltage generator according to a second embodiment of the present invention, and FIG. , FIG. 8 relates to the prior art, FIG. 7 is a longitudinal cross-sectional view of a coaxial multilayer winding type flyback transformer, and FIG. 8 is a circuit configuration diagram showing a high voltage generator according to the prior art. ■... Flyback transformer, 2... Core, 4...
・Low voltage coil, 7... High voltage coil, 8... High voltage tie-out, 9... Horizontal deflection circuit, 15... Flyback power supply, 16... High voltage cable, 17... Cathode ray tube, 21... First detection resistor, 23.55... Fuse (operation stopping means), 24... Second detection resistor, 25... Constant voltage power supply, 27... Differential amplification Circuit (voltage comparison means), 32...Latch circuit (operation stopping means)
. Patent applicant Murata Manufacturing Co., Ltd. Representative Patent attorney Kazu Hirose Production volume
Naoki NakamuraFigure 2Figure 7

Claims (1)

[Claims] A high-voltage generator comprising a low-voltage coil, a high-voltage coil that generates a high-voltage output when a signal is input to the low-voltage coil, and a flyback power supply provided at a low-voltage side end of the low-voltage coil. a first detection means that detects the primary DC input current flowing through the high voltage coil as a voltage e_B; and a high voltage DC output current flowing through the high voltage coil as a voltage e_B.
A second detection means detects as _H, and a DC voltage E connected to the low-voltage side end of the low-voltage coil and cooperates with the first and second detection means to have a relationship of e_B=e_H+E_s.
A DC power supply that applies __s, and the voltages e_B and e_H+
E_s is inputted, and voltage comparison means outputs a signal when the primary DC input current increases abnormally; and operation stop means permanently stops the high voltage generation operation when the signal is output from the voltage comparison means. A high voltage generator characterized by comprising: