JPS58225780A - Preventing circuit for ion spot of cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevention spot, by cutting off a video signal securely and turning off a high-voltage source during power on or off operation, and holding a blanking voltage in a CR time constant circuit until a voltage originating from cathode-ray tube residual characteristics is extinguished. CONSTITUTION:When a switch 18 is turned on, the video signal is applied to the grid of a cathode-ray tube 6 through the operation of a relay 4 and a low- voltage power source 15 generates an output the operation time of the relay 4 after the switch 18 is turned on. A relay 11 operates a specific time after the output of the power source 15 and the high-voltage power source 23 applies an anode voltage to a terminal 24. The output of the power source 15 is passed through a time constant circuit 12 and then applied as the blanking voltage to the grid of the cathode-ray tube 6. Once the switch 18 is turned off, the output of the power source 15 drops a specific time later and the blanking voltage also drops simultaneously. At this time, this voltage rises from negative to the zero potential according to the time constant determined by the output impedance of the time constant circuit 12 and power source 15. This voltage is impressed to the grid to prevent ion spot.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides general display devices using cathode ray tubes, when a normal power switch is turned on and off. Mayu relates to a circuit that prevents ion burning in cathode ray tubes when there is a ranking voltage abnormality or other power supply abnormalities.

[Technical background of the invention and its problems]

Generally, when turning off the power of a display device that uses a cathode ray tube, the electron beam that was deflected on the cathode ray tube loses its deflection energy the moment the power is turned off, so it concentrates at the center of the cathode ray tube. However, a spot-like brightness remains in the center of the cathode ray tube, and ion burn occurs near the center of the cathode ray tube. This is because even though the power is turned off, it takes some time for the charged high voltage to be completely discharged due to the capacitor characteristics of the cathode ray tube itself, and the blanking voltage applied to the cathode ray tube grid. This is because the voltage is no longer applied to the grid at the same time as the power switch is turned on and the potential becomes zero, so the electron beam concentrates at the center of the cathode ray tube and forms a spot.

The following methods were used to solve this problem.

■ A method that sends an electron beam out of the polar ray tube at the moment the switch is turned on.

■ A method using a relay sequence circuit using delay relays.

That is, the method (2) is a method in which the electron beam is deflected to the outside of the front of the cathode ray tube by switching the DC or AC voltage to the deflection coil at the same time as the switch is turned on, thereby preventing ion burnout during the high voltage discharge period. This method requires a separate power source and requires a considerable amount of current to flow through the deflection coil, which has the disadvantage that the circuit configuration becomes large in terms of current capacity. Further, the method (2) above uses a relay with a delay of several seconds to turn off the high voltage input at the same time as the switch is turned off, and then uses a delay relay to delay the blanking voltage for several seconds and then turns off the blanking voltage. In this method, if an abnormality occurs in the power supply and the blanking voltage becomes abnormal, this relay sequence operation will completely break down, so forming a relay sequence circuit requires an additional circuit and becomes complicated. .

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and can be configured with a simple circuit with a small number of parts, and can reliably turn off the video signal and then turn off the high-voltage power supply when the power is turned on and off, thereby preventing the remaining electrode ray tube from remaining. By maintaining the blanking voltage and OR time constant group circuit until the characteristic voltage disappears, it is possible to prevent ion burnout of the cathode ray tube, and furthermore, even when the blanking voltage is abnormal or other low-voltage power supply circuit abnormalities occur, the cathode ray remains unchanged. It is an object of the present invention to provide a cathode ray tube ion burnout prevention circuit capable of preventing ion burnout of the tube.

[Summary of the invention]

The present invention includes a circuit that cuts off the output side of a video amplifier circuit, an 〇R time constant circuit that can supply a blanking voltage to a cathode ray tube for several seconds through a load resistor of the video amplifier circuit,
Consists of the high-voltage power supply circuit for cathode ray tubes, and not only when the power switch is turned on and off during normal use, but also when there is an abnormality in the power circuit, blanking voltage, or other voltage abnormalities, the video signal is turned off. After turning off the high-voltage input voltage, a simple CR time constant circuit that continues to apply the blanking voltage that was previously applied during normal operation is activated at the required time.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

That is, in FIG. 1, a power on/off switch 3 is provided at the output end of a video amplifier circuit 2 having an input end 1 for a video signal.
The grid 7 of the cathode ray tube 6 is connected via the contact 5 of the relay 4 in series. This grid 7 is connected to the anode of a diode 9 via a load resistor 8 of the video amplifier circuit 2, and the cathode of this diode 90 is grounded via a resistor 10 and a relay 11 in series. The anode of the diode 9 is connected to the ground through a capacitor 13 of the CB time constant circuit 12 and connected to the diode 9 through a resistor 14.
The cathode of this diode 9 is connected to the blanking negative DC voltage output terminal of the low voltage power supply 15. The low voltage power supply 15 and the AC or DC input terminal 16
A contact 17 of the relay 4 is inserted and connected between the two. The low voltage power source 15 is connected to a relay drive voltage application terminal 19 via the relay 4 and a power on/off switch 18 in series. Further, the low voltage power supply 15 is provided with other DC output terminals 2o and xx, and is connected to the DC input terminal of a high voltage power supply 23 via the contact 22 of the relay 11, and the output terminal of this high voltage power supply 23 is connected to a cathode line. Anode terminal 2 of tube 6
Connected to 4. The power on/off switches 18 and 3 are interlocked, and one circuit of the switch 3 is used for a circuit for turning on and off the input side of the video signal.

Further, the relay 11 is a relay that operates by detecting the blanking voltage applied to the cathode ray tube 6, and has a contact 22 that cuts off the input voltage of the high voltage power supply 23 when the relay 11 is turned off from the operating state. Furthermore, the relay 4 is activated when the power switch 18 is turned off and the vehicle is running or when an abnormality occurs in the low voltage power source 16. One circuit of this relay 4 is used as a video system relay contact 5 that turns on and off the video signal input line of the cathode ray tube 6, and operates effectively with a time constant determined only by the capacitor 13 and resistor 14 of the CR time constant circuit 12. It was made so that it could be done.

That is, the operation shown in FIG. 1 will be explained for the following cases ① to θ.

(2) The operation when the power switch is turned on and off will be explained with reference to FIG. Figure 2 is a power switch on/off operation timing chart, (1) is a power switch 3, 1
(b) is the output of the video system relay 4, (C) is the low voltage power supply output, (d) is the video signal, (6) is the high voltage power supply manual relay 11, (f) is the blanking voltage, -) shows high pressure residual characteristics.

That is, when the power switch 18 is turned on, this switch 1
8 is turned on, and at the same time, the relay drive voltage applied to the K IJ relay drive voltage application 19 is supplied to the video system relay 4 as shown in FIG. 2 (&). Relay 4 operates as shown in FIG. 2(b). Due to the operation of this relay 4, contact 5
is on, a video signal is applied to the grid of the cathode ray tube 6 as shown in FIG. 2(d). Further, the contact 17 is turned on by the operation of the relay 4, and AC or DC input is applied to the low voltage power supply 15 from the AC or DC input application terminal 16. Therefore, as shown in FIG. 2(c), the low-voltage power supply 15 operates for an operating time T of the relay 4 after the power switch 18 is turned on.
Output is generated with a delay of 1. The output of this low voltage power supply 15 is applied to the high voltage power supply input relay 11, and this relay 11
As shown in FIG. 2(,), the relay 11 operates after a time T after the output of the low voltage power supply 15, and as the contact 22 is turned on by the operation of this relay 11, the DC input from the low voltage power supply 15 is added to the high voltage power supply 23. The high voltage power supply 23 applies a high voltage cathode ray tube anode voltage to the anode terminal 24 of the cathode ray tube 6.

Further, the output of the low voltage power supply 15 is applied to the grid of the cathode ray tube 6 as a blanking voltage as shown in FIG. 2(f) after passing through the time constant circuit 12.

On the other hand, when the power switch 18 is turned off as shown in FIG. 2(,), the video signal input contact switch 3 is turned off and the video signal is no longer supplied as shown in FIG. 2(d). Video system relay 4 as shown in (b)
is turned off. Contacts 5 and 1 are turned off by turning off relay 4.
7 is turned off, and as a result of the contact 17 being turned off, no AC or DC input is applied to the low voltage power supply 15, and the output of the low voltage power supply 15 drops after a time T, as shown in FIG. At the same time as this low voltage power supply 15 is turned off, the blanking voltage also turns off as shown in FIG. 2(f). At this time, the blanking voltage exponentially moves from negative to zero potential according to the CR time constant determined by the capacitor 13 and resistor 14 of the time constant circuit 12 and the output impedance of the low voltage power supply 15. By applying this blanking voltage to the grid of the cathode ray tube 6, ion burnout of the cathode ray tube 6 can be prevented due to the high voltage residual characteristics of the cathode ray tube 6, as shown in FIG. 2(g).

@ The operation in the case of blanking voltage abnormality will be explained with reference to FIG. 3. Figure 3 is an operation timing chart when the blanking voltage becomes abnormal. The output, (d) is a video signal, (,) is the high voltage power supply manual relay 11, (f) is the blanking voltage, and (JK) is the high voltage residual characteristic.

That is, after turning on the power switch 3.18, the process is the same as in case (2), so the explanation will be omitted. Therefore, when the blanking voltage becomes abnormal as shown in Fig. 3(f), the state shown in Fig. 3(f) occurs at point A.
, ), the high-voltage power supply human-powered relay 11 is turned off from the operating state, the contact 22 is turned off, the DC input from the low-voltage power supply 15 to the high-voltage power supply 23 is cut off, and the cathode ray tube anode voltage from the high-voltage power supply 23 is is the anode terminal 24 of the cathode ray tube 6
Avoid joining. Further, when the blanking voltage becomes abnormal, a power abnormality signal from the low voltage power supply 15 is applied to the video system relay 4 to turn off the relay 4. When this relay 4 is turned off, contacts 5 and 17 are turned off,
By turning off the contact 5, the video signal is no longer applied to the grid of the cathode ray tube 6, as shown in FIG. 3(d). Also,
By turning off the contact 17, the p AC or DC input is switched to the low voltage power supply 1.
5, and the output of the low voltage power supply 15 is as shown in Figure 3 (C
) is not output as shown. As soon as the high-voltage power supply manual relay 11 is turned off, the high-voltage output from the high-voltage power supply 23 is discharged as shown by the shaded area in FIG. 3(g). On the other hand, after point A, the blanking voltage moves from a negative voltage to zero potential according to a time constant determined by the capacitor 13 and resistor 14 of the time constant circuit 12 and the output impedance of the low voltage power supply 15. By applying this blanking voltage to the grid of the cathode ray tube 6, it is possible to prevent ion burnout of the cathode ray tube 6 due to the high voltage residual property of the cathode ray tube 6.

θ The operation when there is an abnormality in the low voltage power supply will be explained with reference to FIG. Figure WJ4 is an operation timing chart when there is an abnormality in the low voltage power supply, and (a) is the power switch 3.
, 18, (b) is the output of video system relay 4, (C
) is the low voltage power supply output, (d) is the video signal, (e) is the high voltage power supply manual relay 23, (f) is the blanking voltage, (X) is
Shows high pressure residual properties.

That is, after the power switches 3 and 18 are turned on, the process is the same as in case (2), so the explanation will be omitted. If an abnormality occurs in the low voltage power supply 15 and there is an abnormality other than the blanking voltage, the power supply abnormality signal turns off the video system relay 4 as shown in FIG. 4(b), and the contacts 5 and 1r is turned off. When the contact 5 is turned off, the video signal is no longer applied to the cathode ray tube 6 as shown in FIG. There is no DC output from the power source 15, so the high voltage power source manual relay 11 is turned off as shown in FIG. 4(a), its contact 22 is turned off, and the high voltage power source 23 is turned off, as shown in FIG. 4(g). Like cathode ray tube 6
No anode voltage is applied to. In this case, high voltage remains in the cathode ray tube 6 due to the high voltage residual characteristic, but during this time, the time constant circuit 12 applies a blanking voltage to the grid of the cathode ray tube 6, thereby preventing ion burnout of the cathode ray tube 6. can.

〔Effect of the invention〕

As described above, according to the present invention, when the power is turned on and off, the video signal is reliably turned off and then the high-voltage power is turned off, and the time constant circuit holds the blanking voltage until the voltage due to the residual characteristics of the cathode ray tube disappears. It is possible to prevent ion burning of the tube. Further, even when the blanking voltage is abnormal or other low voltage power supply circuit abnormalities occur, ion burnout of the cathode ray tube can be prevented. Furthermore, this circuit is a simple circuit with a small number of component constants, and can be adapted to circuits where cathode ray tubes have different time constants for different devices by simply changing the time constants of capacitors and resistors.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, and FIG. 2 (
, ) to (2)) are operation timing charts of each part when the power switch according to the present invention is turned on and off, FIG. 3 (,)
~(g) is an operation timing chart when the blanking voltage becomes abnormal according to the present invention, and FIG. 4(a) ~-)
is an operation timing chart when there is an abnormality in the low voltage power supply according to the present invention. 1... Video signal input terminal, 2... Video amplifier circuit, 3.18... Power on/off switching, 4...
Video system relay, 6... Cathode ray tube, 11... High voltage power supply manual relay, 12... Time constant circuit, 15... Low voltage power supply, 16... AC or DC input terminal, 19... Relay Drive voltage application end, 23...high voltage power supply.

Claims (1)

[Claims] A cathode ray tube whose grid is supplied with a video signal, a first power source that supplies voltage to the anode of the cathode ray tube, a second power source that operates by being supplied with alternating current or direct current, and From the second power source! a time constant circuit that is supplied with a ranking signal and supplies an output signal to the grid; and a first switching device that is operated by the plugging signal and is provided in a DC supply line from the second power source to the first power source. The video signal supply line to the grid and the second
a second switch having a contact on an AC or DC supply line to the power source; a third switch connected to and connected to the drive voltage supply line to the second switch and the video signal supply line to the grid, respectively; A fourth switching device.