KR970006125Y1 - Circuit for restriction of high voltage - Google Patents

Abstract

No summary

Description

High pressure limit circuit

1 is an overall circuit diagram showing the prior art

2 and 3 are each waveform diagram according to the operation of FIG.

4 is a circuit diagram showing an embodiment of the present invention

5 and 6 are each waveform diagram according to the operation of FIG.

* Description of the symbols for the main parts of the drawings *

10: rectifying unit 11: test unit

12: voltage division unit 13: reference voltage generation unit

14: comparison unit 15: high-voltage blocking signal generator

R ₆ to R ₁₅ : resistor D ₃ D ₅ : diode

ZD ₁ : Zener Diodes C ₇ , C ₈ , C ₉ : Condenser

L ₅ : coil

The present invention relates to a high-voltage limiting circuit for limiting the increase in high-voltage due to abnormal operation of the circuit, especially in the monitor or TV.

In general, high-voltage is applied to the color TV receiver lamp 20 ~ 30KV, X-rays are emitted when the high pressure rises due to abnormal operation of the circuit, this will be described with reference to Figure 1, the horizontal deflection output unit (1) operates the horizontal output transistor (T ₁ ) and the damper diode (D ₁ ) by a switch to supply the sawtooth current to the deflection coils (L ₁ , L ₂ ) and the collector of the horizontal output transistor (T ₁ ) during the return period. The pulse (VCP) shown in FIG. 2 (a) generated at the stage is applied to the primary coil of the FBT (Fly Back Transformer) 2, and the FBT 2 boosts it to the secondary high voltage coil and outputs the output pulse. Three times rectified and output a DC high voltage of 20 ~ 25KV (Fig. 2 (b)).

However, when the pulse VCP ₁ applied to the primary coil of the FBT 2 rises due to an abnormal operation of the circuit (FIG. 3 (a), the secondary output of the FBT 2 rises above 29 KV. 3b (b)) X-rays are emitted to affect the human body, so as shown in FIG. 1, a high pressure limiting circuit is mounted to limit the increase of the high pressure.

This will be described for a conventional high-voltage limitation circuit is generated in the FBT (2) 2 coil (L ₃₎ for generating a waveform by using the positive (+) pulse generated in the secondary coil, of the coil (L ₃₎ A rectifier 3 for rectifying and smoothing a waveform to output a positive voltage, a voltage divider 4 for distributing a positive voltage rectified and smoothed by the rectifier 3, and a reference voltage for determining a high voltage. Comparing the output of the reference voltage generator 5, the output voltage divider 4 and the output of the reference voltage generator 5 to output a high signal when the output of the reference voltage generator 5 is larger When the presence of a high voltage is detected by the output of the comparator 6 and the comparator 6, a high voltage cut-off signal generator for outputting a high voltage cut-off signal to a power supply (not shown) to stop horizontal oscillation ( 7).

At this time, the rectifier 3 has a resistor (R ₁ ) at _one end of the coil (L ₃ ), a diode (D ₂ ) having an anode end connected to the other end of the resistor (R ₁ ), and a cathode of the diode (D ₂ ). One end is connected to the other end and the other end is composed of a grounded capacitor (C ₃ ), the voltage distribution unit 4 is connected to the output terminal of the rectifier (3) one end and the other end of the inverting input terminal of the comparison unit (6) Resistor R ₂ connected to one end is connected to the inverting input terminal of the comparison unit 6 and the other end is composed of a grounded resistor R ₃ and a capacitor C ₄ , and the reference voltage generator 5 is One end is connected to a microcomputer (not shown in the drawing), the other end is a resistor R ₄ connected to the non-inverting input terminal of the comparator 6, a voltage of 6.3 V is applied to the other end, and the other end is the comparator 6 Resistor (R ₅ ) connected to the non-inverting input terminal of), one end is connected to the non-inverting input terminal of the comparator 6 and the other end is composed of a grounded capacitor (C ₅ ), The high pressure off-signal generation section 7 and the base terminal connected to the cathode terminal of the zener diode (ZD _1), the jaeneo diode (ZD ₁₎ the anode terminal connected to the output of the comparison unit (6), the emitter teodan PNP transistor is applied with a power source (T ₂₎ the emitter of the NPN transistor (T _3), the NPN transistor (T ₃₎ is the power to the PNP transistor (T ₂₎ the collector-stage base terminal is connected and the collector end to the applied teodan An anode end is connected to the cathode end is composed of a diode (D ₃ ) connected to the power supply.

The operation description of the high pressure limit circuit of the prior art configured as described above is as follows.

First, in a normal state, a waveform V _D as shown in FIG. 2C is induced in the coil L ₃ by the secondary coil of the FBT 2, and rectified and smoothed in the rectifying unit 3. The waveform V _D as shown in FIG. 2 d is divided by the resistors R ₂ and R ₃ of the voltage divider 4 (FIG. 2 e). Is applied to the inverting input terminal of.

On the other hand, the reference voltage generator 5 generates a reference voltage higher than a voltage applied to the inverting input terminal of the comparison unit 6 under the control of the microcomputer and applies it to the non-inverting input terminal of the comparison unit 6 ( 2 (f)).

That is, the voltage divider 4 divides the output voltage V _D of the rectifier 3 as in the first equation.

The comparator 6 is applied to the inverting input terminal. The reference voltage generator 5 generates a voltage slightly higher than the inverted input terminal applied voltage of the comparator 6 in the steady state as in the second equation under the control of the microcomputer. So

The non-inverting input terminal of the comparison unit 6 is applied.

Therefore, in the steady state, the output of the comparator 6 becomes high (Fig. 2 (g)), and the transistors T ₂ and T ₃ are also turned off so that the high voltage limiting circuit does not operate. h)).

However, if the circuit is to operate in an abnormal rise in the secondary side output of the FBT (2) As described above, the coil (L ₃₎ voltage induced the first and third lift as shown in (c) (VD ₁₎ to thus rectifying The output waveform VD ₁ of (3) also rises (Fig. 3 (d)), and the output voltage (Fig. 3 (e)) of the voltage distribution section 4 also rises.

Accordingly, the comparison unit 6 compares the output voltage of the voltage divider 4 with the reference voltage of the reference voltage generator 5 (FIG. 3f), thereby reducing the output voltage of the voltage divider 4. When the reference voltage is greater than the reference voltage (Fig. 3 (g)), the transistors T ₂ and T ₃ are turned on to output a high signal to the power supply unit through the diode D ₃ .

Then, the SMPS (Swtching Mode Power Supply) of the power supply unit stopped the oscillation and the secondary voltage of the FBT 2 was cut off to be set off, thereby preventing X-ray generation due to high voltage.

Further, in the prior art, first as shown in FIG negative polarity is generated in the secondary coil of the FBT (2) - a cathode to a coil for generating a waveform by using the pulse (L _4), the coil (L ₄₎ () stage is connected and the anode terminal is configured as a diode (D ₄₎ the diode (D ₄₎ and the anode terminal is connected to one end the other end is grounded capacitor of the (C ₆₎ connected to the grid first terminal of a CRT (Cathode Ray Tube) The grid control unit 8 is further provided to perform the following operation.

A second constant to the coil (L ₄₎ by the primary coil waveform of the FBT (2) is organic, the diode (D ₄₎ and the capacitor (C ₆₎ the diode (D ₄₎ anode terminal is rectified and smoothed in by Applied negative voltage.

The rectified negative voltage applied to the anode terminal of the diode D ₄ is applied to the grid terminal 1 of the CRT to adjust the amount of beam current.

However, when constructing the high pressure limiting circuit, a coil (C ₃ ) is required to detect the high voltage rise of the secondary side of the FBT, and a high pressure is applied to the inverting input terminal of the comparator to test whether the high pressure limiting circuit operates normally when the high pressure is increased. Since it checks the normal operation of the high-voltage limiting circuit by supplying the same power as it has risen, there is a very troublesome problem in producing the power supply equipment.

In FIG. ₁ , reference numerals C ₁ and C ₂ denote capacitors, and R ₆ , R ₇ , R ₈ , and R ₉ denote resistances.

The present invention has been made to solve the above problems, the object of the present invention is to limit the high pressure by detecting the high voltage by using the output negative (-)-voltage of the grid control unit, simplifying the configuration of the circuit, the high pressure limit It is to provide a high voltage limiting circuit that can make it very easy to test whether the circuit works normally.

A characteristic of the high-pressure limiting circuit for achieving the above object is a rectifying unit for rectifying the negative voltage induced on the secondary side of the flyback transformer to a DC voltage to provide a control voltage to the grid end of the cathode ray tube, and the negative side of the secondary side According to the voltage conversion state, a test unit for outputting a voltage having a predetermined level of polarity, a voltage divider for outputting a voltage divided according to the output voltage of the test unit, a voltage comparison unit comparing the voltage and the reference voltage of the cathode ray tube And a high voltage breaking generator for outputting a predetermined pulse signal to the power supply unit according to the output voltage of the comparator when the high voltage rises in the cathode ray tube.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the high pressure limiting circuit of the present invention will be described in detail.

4 is a detailed circuit diagram illustrating an embodiment of the present invention, in which a waveform generated by a coil L ₅ generating a waveform by using a negative (-) pulse generated in a secondary coil of the FBT 2 is negative ( Rectified and smoothed with a DC voltage of-) and connected to the rectifying unit 10 and the rectifying unit 10 to be transmitted to the first grid terminal of the CRT, when the high voltage output of the FBT 2 is 29 KV or less. The test unit 11 outputs a negative voltage when 0 kV and 29 KV is exceeded, and a voltage of 12 V is applied and the output voltage of the test unit 11 varies according to the change of the output voltage value. A voltage divider 12 for outputting a voltage, a reference voltage generator 13 for generating a reference voltage for discriminating a high voltage, a reference of the variable output voltage and the reference voltage generator 13 of the voltage divider 12 Compare the voltage and output a high signal when the output voltage of the voltage divider 12 is greater than the output voltage of the reference voltage generator 13. Comparing unit 14, when the presence of the high pressure is detected by the output of the comparator 14 is configured as a high-voltage cut-off signal generator 15 to output a high-voltage cut-off signal to the power supply to stop the horizontal oscillation.

At this time, the rectifier 10 has a resistor (R ₁₀ ) having one end connected to the coil (L ₅ ), a cathode end of which is connected to the other end of the resistor (R ₁₀ ), and an anode end of the test unit 11 and the CRT. The diode (D ₅ ) connected to the grid terminal 1, the anode end of the diode (D ₅ ) is connected to the other end is composed of a capacitor (C ₇ ) grounded, the test section 11 is one end of the rectifier The other end is configured with a resistor (R ₁₆ ) connected to the voltage divider 12 and the voltage divider 12 has 12V applied at one end to a non-inverting input terminal of the comparator 14. The resistor R ₁₂ having the other end connected thereto, the resistor R ₁₃ having one end connected to the non-inverting input terminal of the comparator 14, and the other end connected to the other end of the resistor R ₁ 1, of the comparator 14 One end is connected to the non-inverting input terminal and the other end is composed of a grounded capacitor C ₈ , and the reference voltage generator 13 has one end connected to the microcomputer. The other end is connected to the inverting input terminal of the comparator 14, R ₁₄ , 6.3V is applied to one end and the other end is connected to the inverting input terminal of the comparator 14 (R ₁₅ ), the comparator One end is connected to the inverting input terminal of (14) and the other end is composed of a grounded capacitor (C ₉ ).

In addition, the high voltage blocking signal generator 15 has the same configuration as the high voltage blocking signal generator 7 of the prior art (FIG. 1) described above.

At this time, the voltage of 12V negative minute and the holding portion 10 to be applied to the resistor (R ₁₂₎ of the distributor (12) (-) of the DC voltage (-VG ₁₎ the voltage difference between the resistance (R ₁₂₎ and the resistance between the The voltage values of the resistors R ₁₁ , R ₁₂ , and R ₁₃ are determined according to the resistance values of R ₁₃ and the resistance R ₁₁ of the test unit ₁₁ , and the secondary high voltage of the FBT 2 is determined. When the output is less than 29KV, that is, when the steady state, the voltage level between the resistor (R ₁₃ ) and the resistor (R ₁₁ ) becomes a positive value. Adjust the resistance (R ₁₁ , R ₁₂ , R ₁₃ ) values to get a negative value.

Further, in a steady state, the voltage VTP ₂ applied to the non-inverting input terminal of the comparator 14 is a constant voltage (0.8V) higher than the voltage VTP ₃ applied to the inverting input terminal (VTP ₂ = VTP ₃ +0.8). V), the output of the reference voltage generator 13 is adjusted by the microcomputer.

The operation of the high-voltage limiting circuit of the present invention configured as described above will be described with reference to FIGS. 5 and 6.

First, in the normal state, the output of the secondary coil of the FBT 2 becomes 25 KV, and the waveform shown in FIG. 5A is induced in the coil L ₅ by the secondary coil of the FBT 2. .

The rectifying unit 10 rectifies and smoothes the waveform induced by the coil L ₅ to a negative DC voltage (-VG ₁ ) and transmits it to the grid 1 terminal of the CRT (FIG. 5 (b)). The beam current of the CRT is adjusted and transmitted to the resistor R11 of the test unit 11.

In this case, the resistance _{(R 11, R 12, R} 13) in accordance with the resistance value adjusted and the voltage level of voltage (VTP) of the amount between the resistor (R ₁₁₎ and a resistance (R ₁₃₎ (FIG. 5 (c)) The voltage VTP ₂ applied from the voltage divider 12 to the non-inverting input terminal of the comparator 14 is equal to that of FIG. 5d, and the reference voltage generator 13 is a microcomputer. The reference voltage VTP ₃ generated by a predetermined voltage lower than the applied voltage VTP ₂ of the non-inverting input terminal of the comparison unit 14 is controlled by FIG. 5 (e) to invert the comparison unit 14. To the input.

Therefore, in the steady state, the output of the comparison unit 14 becomes high (FIG. 5 (f), the high-voltage cut-off signal generator 15 does not generate a high-voltage cut-off signal (Fig. 5 (g)).

However, as described above, when the circuit operates abnormally and the secondary output of the FBT 2 exceeds ≒ 29KV, or 29KV, the voltage induced in the coil L5 rises as shown in FIG. The negative DC voltage of the rectifier 10 also increases in the negative direction (-VD ₁ ) (FIG. 6B).

Therefore, the voltage level between the resistance (R ₁₁₎ and the voltage resistance (R ₁₃₎ of the distributor (12) of the test unit 11 is 0V, or negative, and the voltage value (VTP ₁ ') of the (() In FIG. 6 (c)), the voltage VTP2 'applied to the non-inverting input terminal of the comparator 14 in the voltage divider 12 is lowered (FIG. 6 (d)).

Since the output voltage of the reference voltage generator 13 is the same as in the normal state (VTP ₃ ) (FIG. 6 (e)), the comparison unit 14 is the voltage divider 12 and the reference voltage generator ( By comparing the voltages of 13 and outputting a low when the reference voltage VTP ₃ of the reference voltage generator 13 is greater than the voltage VTP ₂ ′ of the voltage divider 12 (FIG. 6 (f)). The transistor T ₂ of the high voltage blocking signal generator 15 is turned on.

Accordingly, the transistor T ₃ is also turned on to output a high signal (Fig. 6 (g)) to the power supply through the diode D ₃ so that the SMPS of the power supply stops oscillation and the secondary voltage of the FBT 2 is stopped. It is blocked and put into a cell-off state, which prevents X-ray generation due to high pressure.

In addition, to test whether the high-voltage limiting circuit of the present invention operates normally, the resistor R ₁₁ and the resistor R ₁₃ are grounded using a wire.

Then, as described above, the secondary output of the FBT 2 has the same condition as ≒ 29 KV, and the output of the voltage divider 12 falls, so that it is possible to know whether the high voltage limiting circuit operates normally when the high voltage rises. .

As described above, the present invention can simultaneously perform the high pressure limiting and CRT grid control roles by using one coil and the rectifier circuit, and can easily perform the test of the high pressure limiting circuit, thereby contributing to cost reduction and productivity improvement. .

Claims (4)

(Correction) a rectifying unit for rectifying the negative voltage induced on the secondary side of the flyback transformer to a DC voltage and providing the control voltage to the grid terminal of the cathode ray tube; A test unit configured to output a voltage having a predetermined level of polarity according to the secondary negative voltage conversion state; A voltage divider for outputting a divided voltage according to the output voltage of the test unit; A comparison unit which compares the voltage of the voltage divider with a reference voltage and determines whether a high voltage is increased in the cathode ray tube; And a high voltage cut-off signal generator configured to output a predetermined pulse signal according to the output voltage of the comparator when the voltage rises in the cathode ray tube. (Correction) The high voltage limiting circuit according to claim 1, wherein the rectifying portion is connected between the secondary coil of the flyback transformer and the test portion. (delete) (delete)