JPS5828948B2 - Atsushi Atsukiyousouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply voltage supply device particularly useful for use in television receivers.

In television receivers, a high voltage is required to accelerate the electron beam in the cathode ray tube, but if this high voltage is abnormally high, a discharge occurs within the cathode ray tube, and the resulting abnormal voltage is transmitted to the surrounding circuits. This often causes damage and deterioration of circuit elements.

Further, acceleration of the electron beam by an abnormally high voltage may easily generate harmful X-rays.

Conventionally, various protection devices have been devised to detect or prevent the occurrence of this type of abnormally high pressure, but many of the conventional devices have complex configurations, and when the protection device system itself is malfunctioning, If an abnormally high voltage were to occur, there were many cases where there was no way to prevent it.

The present invention eliminates the drawbacks of the conventional device as described above, and provides a device that prevents images from being viewed under abnormally high voltage as described above even when the protection system fails. It is something to do.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In the figure, a power supply circuit 1 that generates a first power supply voltage is connected to a power switch 2 provided in the television receiver.
It operates by turning on the power and supplies power supply voltage to the necessary circuits of the television receiver.

The first power supply voltage from the power supply circuit 1 is passed through a power supply voltage adding circuit 3 to a negative resistance circuit 4 having a non-linear power cutoff function.
guided by.

Power from the power source is supplied via the negative resistance circuit 4 to the horizontal oscillation circuit 5, which is a pulse generation source.

According to this configuration, immediately after the power switch 2 is turned on, only the first power supply voltage is obtained as the output of the power supply voltage adding circuit 3, and above a certain applied voltage, a negative resistance characteristic is exhibited. The resistance circuit 4 operates in a positive resistance region and applies a power supply voltage to the horizontal oscillation circuit 5 to supply power.

The power supply voltage applied to the horizontal oscillation circuit 5 in this state is lower than that during normal operation, but is selected to be sufficient to allow the horizontal oscillation circuit 5 to perform oscillation.

The oscillation output of the horizontal oscillation circuit 5 drives the horizontal output circuit 6 via one drive amplification stage as required.

The first power supply voltage from the power supply circuit 1 is directly applied to the power supply of the horizontal output circuit 6, and a flyback transformer T is normally connected to the output of the horizontal output circuit 6.

The horizontal pulse supplied from the horizontal oscillation circuit 5 is boosted by the flyback transformer 7 of the horizontal output circuit 6 and becomes a high voltage pulse.

A high-voltage rectifier circuit 8 is connected to the flyback transformer 7, which rectifies and smoothes the high-voltage pulse to obtain at its output terminal 9 an anode voltage necessary for accelerating the electron beam of the cathode ray tube.

On the other hand, a pulse voltage proportional to the high voltage pulse voltage is taken out from the flyback transformer 7, and the power supply voltage adding circuit 3
supply to.

The power supply voltage adding circuit 3 rectifies the pulse voltage to obtain a second power supply voltage, and superimposes and adds the first power supply voltage and the second power supply voltage.

The state in which the second power supply voltage is added to the first power supply voltage in this manner is the steady state of the power supply voltage supplied to the horizontal oscillation circuit 5 via the negative resistance circuit 4.

At this time, the horizontal oscillation circuit 5 enters a predetermined oscillation frequency range.

A part of the flyback pulse from the flyback transformer 7 is further supplied to the AFC circuit 11, where it is shaped into a sawtooth wave, and compared in phase with the horizontal synchronizing signal supplied to the input terminal 10 of the AFC circuit 11. A control voltage for controlling the oscillation frequency of the horizontal oscillation circuit 5 is generated.

In order to explain the operation of this device in more detail, FIG. Give an example.

FIG. 2a shows the voltage at the input of the negative resistance circuit 4 of the power supply voltage supplied to the horizontal oscillation circuit 5, and FIG. 2a shows the corresponding change characteristics of the high voltage.

In FIG. 2, when the power switch 2 is turned on at time to, only the first power supply voltage is applied to the horizontal oscillation circuit 5 via the power supply voltage addition circuit 3 and the negative resistance circuit 4, and increases toward the voltage E1. do.

When the power supply voltage reaches approximately E□, the horizontal oscillation circuit 5 starts oscillating.

However, the frequency range of this oscillation frequency is limited to the AFC circuit 11.
It is at a frequency that cannot be synchronized to the horizontal synchronization signal despite the operation of the

In other words, this indicates that a steady oscillation state has not been reached.

On the other hand, the horizontal output circuit 6 driven to 1 by the output of the horizontal oscillation circuit 5 generates a flyback pulse through the flyback transformer 7.

A part of this flyback pulse is rectified by the power supply voltage adding circuit 3 to generate a second power supply voltage, which is added to the first power supply voltage.

In this state, the power supply voltage supplied to the horizontal oscillation circuit 5 almost reaches the voltage E2 at time t2 as shown in FIG. Oscillates at a synchronized frequency.

In other words, a steady oscillation state is reached. High voltage is also the second
As shown in the figure, the time t when the horizontal oscillation circuit 5 starts oscillating,
It rises more gradually and reaches time t2fVo.

A steady high voltage output is obtained after time t2 (t2-t
a) Next, a case where the high voltage becomes higher than normal for some reason after time t3 as shown in FIG. 2 will be explained.

Generally, the high voltage is proportional to the flyback pulse, but in the present invention, the pulse voltage supplied to the power supply voltage adding circuit 3 and used to generate the second power supply voltage is designed to have a proportional relationship with the high voltage. ing.

Therefore, the second power supply voltage changes in proportion to changes in the high voltage.

That is, when an abnormally high voltage occurs, the second power supply voltage also increases, and is applied as a power supply voltage that brings the negative resistance circuit 4 into the negative resistance region.

Therefore, the supply of power to the horizontal oscillation circuit 5 is cut off, so horizontal oscillation is stopped and abnormally high voltage is prevented from occurring.

FIG. 3 is a diagram for explaining the operation of the negative resistance circuit 4.
The curve shown in the figure shows the applied voltage vs. current characteristic of the negative resistance circuit 4, and the point O-C on the curve is a positive resistance region, and the area to the right of point C is a negative resistance region.

Now, when operating with only the first power supply voltage, the load characteristic line becomes A and the circuit operates at point A, supplying a voltage of (EI E4) and a current of ■1 to the horizontal oscillation circuit 5.

The horizontal oscillation circuit 5 starts oscillating, a flyback pulse is generated, and when the second power supply voltage is obtained, the voltage applied to the negative resistance circuit 4 becomes E2, and a stable state is established with point B as the operating point.

The magnitude of the second power supply voltage at this time is (E2 El).

Here, if a high voltage higher than normal occurs and the corresponding second power supply voltage increases to U) above (E3 El), the operating point will change to point B-)CL'->D. move, cut off the current to the horizontal oscillation circuit 5, and stop oscillation.

When the horizontal oscillation stops, the flyback pulse disappears and the operating point moves to point E.

As mentioned above, this device only uses A when the power switch 2 is turned on.
It operates at point B and immediately enters a steady state with point B as the operating point.

FIG. 4 is a circuit diagram of a specific embodiment of the present invention.

In FIG. 4, a power supply circuit 1 supplies a first power supply voltage to the circuit by turning on a power switch 2. In FIG.

The power supply voltage adding circuit 3 includes a capacitor 31 and a diode 32.
, and a capacitor 33, which together with the tertiary winding of a flyback transformer 7, which will be described later, provides power supply voltage addition means.

As a specific example of the negative resistance circuit 4 shown in FIG. 1, in FIG. 4, a series connection circuit of a constant voltage element 42 and a negative resistance element 41 is used.

As a representative example of the negative resistance element 41, a lambda type transistor (trade name of Matsushita Electronics Co., Ltd.) is most convenient and effective.

Here, a negative resistance element 41 and a constant voltage element 42 are used so that the voltage versus current characteristics shown by the curve in FIG. 3 can be obtained.

Therefore, immediately after turning on the power switch 2, the power supply voltage of the horizontal oscillation circuit 5 is high enough to allow the horizontal oscillation circuit 5 to oscillate.
can be supplied to

Note that in FIG. 3, point 07 indicates the zero point of the voltage versus current characteristic only in the negative resistance element 41.

The horizontal oscillation circuit 5 includes a transistor 51. Oscillation transformer 52
, resistor 55 constitute a blocking oscillator.

The oscillation transformer 52 is equipped with a winding 53 and a winding 54, which are connected to provide a feedback operation necessary for oscillation.

The oscillation output is taken out from the winding 57 and supplied to the horizontal output circuit 6 at the next stage.

The horizontal output circuit 6 includes 1 drive transistor 61° drive transformer 62, horizontal output transistor 3, damper diode 64, resonance capacitor 65, horizontal deflection coil 66,
The collector of the drive transistor 61 is supplied with the first power supply voltage via the drive transformer 62, and the collector of the horizontal output quadrant transistor 3 is also supplied with the primary winding 72 of the flyback transformer 7. A first power supply voltage is supplied via the first power supply voltage.

The flyback pulse generated across the primary winding 72 of the flyback transformer 7 is boosted by the high voltage winding 73, rectified by the high voltage rectifier circuit 8 consisting of a diode 81 and a capacitor 82, and the resulting DC high voltage is It is supplied from the output terminal 9 to the anode of a cathode ray tube (not shown).

As described above, the high voltage generating means includes the horizontal oscillation circuit 5, the horizontal output circuit 6, the flyback transformer 7, and the high voltage rectifier circuit 8.

The pulse voltage induced in the third winding 74 of the flyback transformer 7 is wound so as to be very similar to the high voltage pulse generated in the high voltage winding 73.

That is, the third winding 74 is wound around the transformer core 71 so as to be loosely coupled to the primary winding 72 and tightly coupled to the high voltage winding 73.

When the power switch 2 is turned on, the horizontal oscillation circuit 5 starts oscillating, and when a flyback pulse is generated in the primary winding 72 of the flyback transformer 7, a pulse voltage is also induced in the third winding 74.

One end of the third winding 74 is connected to the power supply circuit 1 and short-circuited with the capacitor 31, so that when the pulse voltage obtained from the third winding 74 is rectified and smoothed by the diode 32 and the capacitor 33, The resulting voltage becomes the second power supply voltage and is added to the first power supply voltage.

Therefore, the power supply voltage adding means is constituted by the power supply voltage adding circuit 3 and the third winding 74 of the flyback transformer 7.

When a steady power supply voltage starts to be supplied from the output of the power supply voltage adding circuit 3 to the horizontal oscillation circuit 5 through the series circuit of the constant voltage element 42 and the negative resistance element 41, the oscillation frequency of the horizontal oscillation circuit 5 becomes equal to that of the AFC circuit 11. The operation results in a range in which pull-in synchronization can be achieved with respect to the horizontal synchronizing signal applied to the input terminal 10.

That is, a part of the flyback pulse is fed back to the AFC circuit 11 from the tap of the high voltage winding 73 of the flyback transformer 7, so the AFC circuit 11 performs a phase discrimination operation and supplies an output signal to the horizontal oscillation circuit 5. Control the oscillation frequency.

Therefore, in the steady state, the oscillation frequency of the horizontal oscillation circuit 5 is sufficiently synchronized with the horizontal synchronization signal frequency.

Here, the negative resistance element 41 has an input terminal connected to the constant voltage element 42 and an output terminal connected to the horizontal oscillation circuit 5.

The constant voltage element 42 is designed to reduce variations in voltage versus current characteristics due to deviations of the negative resistance element 41.

Now, considering the case where the negative region inrush current of the negative resistance element 41 increases from Ic to IB in the voltage vs. current characteristic curve of the negative resistance circuit 4 shown in FIG. 5, the operating voltage corresponds to Ec. increases from to EB.

The rate of change in the operating voltage at this time is given by Es-Ec/Ec.

Next, when the voltage between both ends of the constant voltage element 42 is made zero, that is, it is short-circuited, and the number of turns of the third winding 74 is adjusted so that the power supply voltage supplied to the horizontal oscillation circuit 5 is the same as above. Considering this, the negative resistance circuit 4 becomes only the negative resistance element 41, and the zero point of the voltage vs. current characteristic curve moves from point 0 to point 07.

Therefore, the rate of change in operating voltage at this time is EB-Ec/
It is given by Ec-Ez, and is larger compared to the case where the constant voltage element 42 described above is arranged like this.

Ez corresponds to the voltage between o and o' in FIG. 5, and is the voltage between both ends of the constant voltage element 42.

Further, the negative overhead inrush current of the negative resistance element 41 changes from Ic to I
Even when the operating voltage decreases to s, if the constant voltage element 42 is provided, the rate of change in the operating voltage becomes smaller as in the above explanation.

FIG. 6 illustrates the rate of change of the voltage versus current characteristic with respect to the deviation of the negative resistance element 41 obtained in the example of FIG. 4.

In the figure, curve A shows the embodiment of the present invention, and curve B shows the case where the constant voltage element 42 is short-circuited.

As is clear from these results, when the constant voltage element 42 and the negative resistance element 41 are operated in combination, variations in operating voltage can be reduced.

This makes it possible to significantly reduce the influence of the deviation of the negative resistance element 41 on the abnormal high voltage sensing operation.

In the embodiment of the present invention described above, the horizontal oscillation circuit 5
Although the case where the resistor 55 is included in the
The location 5 is not limited to the embodiment shown in FIG. 4, but can be any location between the power supply circuit 1 and the negative resistance circuit 4.

In addition, although the horizontal oscillation circuit 5 has been described as an example of a target to which the power supply voltage is supplied through the negative resistance circuit 4, the power supply voltage is supplied to the drive transistor 61 or the AFC circuit 11 in FIG. 4 through the negative resistance circuit 4. It is also possible to use a circuit configuration that supplies .

In either case, the pulse generation of the flyback pulse voltage intended by the present invention can be interrupted or stopped in the event of an abnormality.

FIG. 7 is a circuit diagram of another embodiment of the present invention, and is a power supply circuit 1.
An application example is shown in which a resistor 55 is installed between the power supply voltage adding circuit 3 and the power supply voltage adding circuit 3.

As described above, the present invention simplifies the circuit by inserting a negative resistance circuit consisting of a series connection circuit of a negative resistance element and a constant voltage element into the power supply path from the power supply voltage addition circuit to the horizontal pulse oscillation circuit. The present invention is practical, and can stably perform abnormally high voltage prevention or sensing operations even with variations in the elements used, and can provide a reliable and highly reliable device.

[Brief explanation of the drawing]

Fig. 1 is a basic block diagram of a power supply voltage supply device in an embodiment of the present invention, Fig. 2 a and b are voltage waveform diagrams for explaining the operation of the embodiment, and Fig. 3 is used in the embodiment. FIG. 4 is a circuit diagram of a specific embodiment of the present invention, and FIG. 5 is an example of voltage versus current characteristics with respect to deviation of the negative resistance element used in the present invention. 6 are characteristic curve diagrams for explaining the characteristics obtained by the present invention, and FIG. 7 is a circuit diagram of another embodiment of the present invention. 1... Power supply circuit, 2... Power switch, 3... Power supply voltage addition circuit, 4... Negative resistance circuit, 5...・Horizontal oscillation circuit, 6...
...Horizontal output circuit, 7...Flyback transformer, 8...High voltage rectifier circuit, 41...Negative resistance element, 42... Constant voltage element .

Claims (1)

[Claims] 1. A horizontal pulse oscillation circuit that operates based on a horizontal synchronization signal, and a horizontal output means that is connected to the horizontal pulse oscillation circuit and includes a flyback transformer that generates a high voltage pulse to obtain a high voltage output to be supplied to a cathode ray tube. a power supply circuit that obtains a first power supply voltage; a power supply voltage adding circuit that rectifies the pulse voltage obtained from the flyback transformer to obtain a second power supply voltage and superimposes and adds the first power supply voltage; A power supply voltage characterized by comprising a negative resistance circuit consisting of a series connection circuit of a constant voltage element and a negative resistance element connected in a power supply path from the power supply voltage addition circuit to the horizontal pulse oscillation circuit. Feeding device.