JPS5842993B2 - Deflection yoke arc prevention circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for preventing arcing between a live part of a deflection yoke and a chassis in a television receiver.

The term "charged part of the deflection yoke" used herein is a term used in the Electrical Appliance and Material Control Law, and refers to a part of the deflection yoke that is connected to the 10B power supply side.

FIG. 1 shows a part of a conventional horizontal deflection circuit including a deflection yoke arc prevention circuit and its power supply.

In FIG. 1, 1 indicates an input terminal for an unstable rectified voltage.

The part 23 surrounded by the dotted line is a well-known series type transistor constant voltage circuit, 9 is a control transistor, 10 is a transistor for error voltage amplification, 14 is a Zener diode for reference voltage, and 2, 3° 4 is for bias. Resistors 5 and 6 are voltage dividing resistors for detection voltage, and 16 is a ripple removal capacitor.

Since the operation of this constant voltage circuit is well known, the description thereof will be omitted, but the unstable rectified voltage applied to the input terminal 1 is made constant and is supplied to the horizontal deflection circuit as a 10B voltage.

The 7.8 resistors are for dividing the 10B voltage and supplying the voltage to the 22 horizontal oscillation circuits.

13 is a horizontal output transistor, and 20 is a drive transformer thereof, which is driven by the oscillation output of the horizontal oscillation circuit 22.

18 is a resonant capacitor, and 13 transistors are O
When it is turned FF, it resonates with the 19 deflection yoke horizontal winding (hereinafter abbreviated as DY), and a high pulse voltage is generated at the collector of the 13 transistor.

At this time, a high voltage is applied to both ends of DY 19.

The high pulse voltage is then stepped up by the flyback transformer 21 to generate a high voltage on the secondary side of the flyback transformer 21.

IT is a figure 8 correction capacitor that resonates with DY 19 and shapes the waveform of the deflection current flowing through DY 19.

The transistor 11.12 is connected to a thyristor, and once it is turned on, it will not reach 0FFL unless the current is below the holding current or a reverse bias is applied.

When an arc occurs between both ends of DY 19 or between the live part of DY 19 and the chassis, diode 15 will
This is to detect the negative voltage generated in the figure 8 correction capacitor.

The reason why negative voltage is generated in the S-shaped correction capacitor IT is currently unclear, but if a short circuit occurs due to an arc between both ends of DY19 or its live part and the chassis (earth), the negative voltage will pass through the eight-shaped correction capacitor 17. It is considered that the resonance state of the path changes, the peak-to-peak value of the voltage across the figure-8 correction capacitor 11 increases, and a negative voltage is generated.

First, let's consider the case where an arc occurs at both ends of DY in No. 19. Due to the occurrence of the arc, a negative voltage is generated in the figure 8 correction capacitor No. 17 as described above.
The diode No. 5 becomes conductive, so the base of the No. 11 transistor drops, and the No. 11 transistor turns on.

Then, base current also flows through the bases of the 12 transistors, and the 12 transistors are also turned on in an instant.

When the transistors 11 and 12 turn on, the power supply voltage of the horizontal oscillation circuit 22 drops, so the oscillation stops and the 1
The high pulse voltage is no longer applied to the collector of the transistor No. 3, and the voltage becomes the rectified voltage at the input terminal 1. Since no high voltage is applied to both ends of the transistor D, arcing stops.

Here, even if both ends of DY 19 are short-circuited (for some reason), the voltage is 10B (at this time, it is almost the rectified voltage of input terminal 1).

) does not drop, so a current higher than the holding current flows through the transistor 1L12, and the power supply voltage of the horizontal oscillation circuit 22 remains low, and oscillation remains stopped, so a high current flows through the collector of the transistor 13. Since no pulse voltage is generated and no high voltage is applied to both ends of DY 19, no arc occurs.

However, if an arc occurs between the charged part of DY 19 and the chassis, the transistor 12 turns on as described above, but when the arc occurs, the 10B voltage is almost OV.
Since the current flowing through the 11°12 transistor is less than the holding current, when the arc stops, lL1
Since the transistor No. 2 is turned off, the horizontal oscillation circuit No. 22 oscillates again, and a high pulse voltage is generated at the collector of the transistor No. 13, causing an arc.

While repeating these operations, in the worst case, 19 DYs will burn, creating a risk of fire, which is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit that eliminates the above-mentioned drawbacks of the prior art and prevents arcing between the live portion of the deflection yoke and the chassis.

The present invention provides a deflection yoke in a circuit that detects the occurrence of an arc when an arc occurs at the deflection yoke, and turns on a transistor connected to a thyristor or a thyristor connected between the power supply voltage of a horizontal oscillation circuit and the ground to prevent the occurrence of an arc. If an arc occurs between the live part of the thyristor and the chassis, a circuit is provided to keep the current flowing through the thyrisk or transistor above the holding current, and the transistor connected to the thyrisk or thyristor is always turned on to prevent the occurrence of an arc. .

Hereinafter, the present invention will be specifically explained with reference to embodiments illustrated in the drawings.

FIG. 2 shows one embodiment of the present invention.

In FIG. 2, the same parts as in FIG. 1 are given the same numbers.

Further, explanations of parts whose operations are the same as those in FIG. 1 will be omitted.

In this circuit, the bias resistor 4 for making the 14 Zener diodes into the Zener region is connected to the rectified voltage side of the input terminal 1, although it was connected to the 10B voltage side in the prior art shown in FIG.

Further, the Zener voltage of the 14 Zener diodes is set lower than the power supply voltage of the 22 horizontal oscillation circuits.

Therefore, the newly added 24 diodes are normally 0FF.
L, there.

Here, if an arc occurs between the charged part of DY 19, that is, the collector of transistor 13, and the chassis, the power supply voltage of horizontal oscillation circuit 22 drops to approximately Ov.

However, since the rectified voltage at the input terminal 1 does not drop, a bias is applied to the Zener diode 14 through the resistor 4, and a Zener voltage is generated.

Therefore, the diode 24 is ONL, the Schener voltage is applied to the transistor 11.12, a current higher than the holding current flows, the horizontal oscillation circuit 22 stops, and the collector voltage of the transistor 13 is almost the same as the rectification of input terminal 1. voltage.

Therefore, in the past, a high pulse voltage was applied between the live part of the 19 DY and the chassis, making it easy for arcs to occur, but with the circuit configuration of the present invention, the 19 DY
Once an arc occurs between the live part of the DY and the chassis, the voltage will always be below the rectified output voltage of 1, which can prevent the occurrence of an arc.Also, using the rectified voltage of input terminal 1 as the power source, an arc will not occur. However, the energy is smaller than that of the conventional method, and combustion of 19 DY can be prevented.

FIG. 3 shows another embodiment of the invention.

In FIG. 3, the same parts as in FIG. 2 are given the same numbers.

In Fig. 2, 14 Zener diodes, which serve as the reference voltage for voltage control, are used to prevent power consumption loss, but if power consumption loss is allowed, input terminal 1 should be connected as shown in Fig. 3. Dividing the rectified voltage with a 25°26 resistor, 2
Even if the voltage across the resistor 6 is lower than the power supply voltage of the horizontal oscillation circuit 22 and the circuit is connected with 24 diodes, the same effect as in the circuit configuration shown in FIG. 2 can be obtained.

Furthermore, the same effect can be obtained by using Cyrisk instead of the transistor 1L12 in FIGS. 2 and 3.

As described above, according to the present invention, by adding a simple circuit to the conventional deflection yoke arc prevention circuit, it is possible to prevent arc generation between the live part of the deflection yoke and the chassis and improve safety. I can do it.

[Brief explanation of drawings]

FIG. 1 shows a conventional horizontal deflection circuit including a deflection yoke arc prevention circuit and its power supply circuit. 2 and 3 show respective embodiments of the deflection yoke arc prevention circuit according to the present invention. 1... Unstable rectified voltage input terminal, 4...
・Bias resistor, 11, 12...Transistor connected to thyristor, 18...Resonance capacitor, 19...Deflection yoke horizontal winding, 22...
... Horizontal oscillation circuit, 23 ... Constant voltage power supply circuit, 24 ... Zener diode for reference voltage, 2
5, 26... Resistor for voltage division.

Claims (1)

[Claims] 1. If an arc occurs in the deflection yoke in the deflection circuit of a television receiver where the unstable rectified voltage is made constant by a constant voltage power supply circuit and used as a 10B voltage, the occurrence of the arc is detected and the 10B voltage is In a circuit that prevents arcing by stopping oscillation by turning on a thyristor (or transistor connected to thyristor) connected between the power supply voltage of a horizontal oscillation circuit obtained by dividing the voltage of If an arc occurs between the thyristor and the chassis, a circuit is provided that utilizes the unstable rectified voltage to maintain the current flowing through the thyristor above the holding current, and the thyristor is always turned on to prevent the occurrence of an arc. A deflection yoke arc prevention circuit featuring: