JPH0516767Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high voltage stabilizing circuit used in television receivers and the like.

[Conventional technology]

Traditionally, in television receivers, etc.
A high voltage generation circuit as shown in FIG. 2 is employed.

In this high voltage generation circuit, the NPN type transistor 1 is turned on and off by applying a horizontal drive pulse b from the horizontal drive circuit 10 to its base. A cathode and an anode of a diode 2 are connected to the collector and emitter of the transistor 1, respectively, a capacitor 3 is connected in parallel to the diode 2, and a series circuit of a large-capacity capacitor 4 and a horizontal deflection coil 5 is connected. are connected in parallel. A power input terminal 11 is connected to the collector of the transistor 1 from a DC power supply (not shown).
A DC voltage +Vcc is applied through the emitter, and the emitter is grounded through the primary coil of the flyback transformer 6. One end of the secondary coil of the flyback transformer 6 is grounded, and there is a connection between the other end and the ground.
A high voltage rectifier circuit consisting of a diode 7 and a capacitor 8 for supplying a positive high DC voltage is connected to the output terminal 9.

The operation of the high voltage generating circuit as described above will be explained with reference to FIG.

In Figures 3a and 3b, Figure a shows the deflection coil 5.
Figure b is a waveform diagram of a horizontal drive pulse applied to the base of transistor 1.
The period from time T ₁ to _{T 2} in FIG. 3 is the latter half of the scanning period, and the transistor 1 is forward biased and turned on. Further, it is assumed that the capacitor 4 has already been charged to the level of the power supply voltage +Vcc. Therefore, during this period, the deflection coil 5
A current increasing linearly in the positive direction is supplied from the capacitor 4 through the transistor 1, and the time
It reaches its maximum value at T ₂ .

The period from time T ₂ to T ₃ is the first half of the retrace period, and the transistor 1 is turned off by the negative pulse, and its collector current becomes zero, but the current in the deflection coil 5 does not immediately become zero; The back electromotive force decreases while charging the capacitor 3.

The period from time T ₃ to _{T 4} is the latter half of the retrace period, and the deflection coil 5 releases the accumulated power, the back electromotive force decreases, and, contrary to the above, current is supplied from the capacitor 3. , this current increases in the negative direction.

Deflection coil 5 during the period from time T ₂ to T ₄
The slope of the current waveform can be determined by the circuit constant of the parallel resonant circuit formed by the capacitor 3 and the deflection coil 5, and is thereby set to have a steep slope.

Next, at time T ₄ , the current flowing through the deflection coil 5 reaches a negative maximum value and then begins to decrease.
The back electromotive force caused by the deflection coil 5 at this time is
The direction is opposite to that during the period T ₂ to T ₄ , and as a result, diode 2 conducts and turns on, so
A parallel resonant circuit as described above is not formed, and the current in the deflection coil 5 decreases with a gentle slope similar to the period from time T ₁ to _{T 2} . After the current in the deflection coil ₅ reaches zero at time T5,
Repeat the operations from T ₁ onwards.

Therefore, a sawtooth wave current as shown in FIG. 3a flows through the deflection coil 5. Here, time T ₂ ~
The back electromotive force generated in the deflection coil 5 during the period _T4 as described above is applied as a flyback pulse to the primary side of the flyback transformer 6, producing a high pulse voltage on its secondary side. This pulse voltage is rectified and appears at the high voltage output terminal 9 as a high voltage DC voltage _VH .

By the way, this high voltage DC voltage _VH is not stabilized, so if stability is required, a high voltage stabilizing circuit as shown in FIG. 4 is used.

In FIG. 4, components corresponding to those in FIG. 2 are given the same reference numerals, and their explanations will be omitted.
In the circuit shown in FIG. 4, unlike the circuit shown in FIG. 2, a control transformer 2 is connected between the emitter of the transistor 1 and the primary winding of the flyback transformer 6.
6 secondary windings are connected. Power input terminal 11
are connected to the cathodes of diodes 22 and 23, and the anodes of these diodes are connected to one and the other terminals of the primary winding of the control transformer 26, respectively, and are connected to the cathodes of diodes 24 and 25, respectively. be done. The anodes of diodes 24 and 25 are connected to the emitter of transistor 1 and the ground terminal, respectively. A switch 27 that is turned on and off by a control circuit 28 is connected in parallel to the diode 25. A resistor 2 is connected between the high voltage output terminal 9 and the ground.
A resistive voltage divider circuit formed by resistors 29 and 30 is connected between the power supply input terminal 11 and ground to generate a reference voltage. These sample voltages and reference voltages are connected to input terminals of the control circuit 28. The control terminal of the control circuit 28 includes
The divided voltage output from the intermediate tap of the primary winding of the flyback transformer 6 is applied as a timing pulse.

Next, the operation of the high voltage stabilizing circuit having the above configuration will be explained. In this case, similar to the circuit shown in FIG. 2, a high voltage output voltage V _H appears at the high voltage output terminal 9 and is divided by resistors 20 and 21 to obtain a sample voltage. This sample voltage is compared with a reference voltage obtained by dividing the power supply voltage Vcc in a control circuit 28, and the switch 27 is controlled to be turned on or off depending on the error.

Now, if the switch 27 is turned on during the period when the transistor 1 is turned on, the control transformer 26 is turned on.
A linearly increasing current flows through the next winding coil via the diode 24. This current is
It continues to increase until transistor 1 turns off at T ₂ . Between times T ₂ and _{T 4} , transistor 1 is turned off, and as in the circuit shown in FIG.
A flyback pulse is generated from the deflection coil 5, and a portion of this flyback pulse is applied as a timing pulse to the control circuit 28 from the flyback transformer 6 through its intermediate tap.
This timing pulse causes the control circuit 28 to
Switch 2 immediately after transistor 1 turns off
Turn off 7. Then, the power energy accumulated in the primary coil of the control transformer 26 becomes a back electromotive force and generates a large control pulse voltage in the secondary coil, causing the flyback transformer 6 to generate a large control pulse voltage.
is applied to the primary coil of This period is also the period during which the flyback pulse is applied from the deflection coil 5 to the flyback transformer 6, as described above. Therefore, the flyback transformer 6 includes a second
In a normal high voltage generation circuit as shown in the figure,
A control pulse voltage as described above is added to the flyback pulse applied to the flyback transformer 6.

This control pulse voltage becomes larger the longer the switch 27 is kept closed. Therefore, when the sample voltage is smaller than the reference voltage, the switch 27 is turned on earlier, and when it is larger, the switch 27 is turned on later, thereby controlling the high voltage output voltage to a substantially constant value. be done. The control circuit 28 operates to determine the timing at which the switch 27 is turned on as described above.

[Problem that the invention attempts to solve]

However, in the high voltage stabilization circuit described above,
The load on transistor 1 changes depending on the operating conditions for high voltage stabilization, and as a result, even if the high voltage output is stable, the deflection current in deflection coil 5 changes, causing fluctuations in the raster size of the television receiver. There are some difficulties that arise.

Therefore, an object of the present invention is to provide a high voltage stabilization circuit that can minimize such variations in raster size.

[Means for solving the problem]

The high voltage stabilizing circuit according to the present invention includes a first switch that is turned on and off by the output of the horizontal drive circuit between the power supply and one end of the first choke coil, and two switches that are connected in parallel to the first switch. a deflection circuit section that connects a first diode and a first capacitor, and connects a series circuit of a first large-capacity capacitor and a horizontal deflection coil in parallel to the first capacitor; A second switch is provided between one end of the primary winding of the back transformer and the secondary winding of the control transformer, which is turned on and off by the output of the horizontal drive circuit. A second diode and a second capacitor are connected in parallel to each other, and a series circuit of a second large capacitance capacitor and a second choke coil is connected in parallel to the second capacitor. A high-voltage pulse generation circuit section that accumulates power during the scanning period through on-off operation and emits high-voltage pulses during the retrace period; and a high-voltage pulse generation circuit section that rectifies and smoothes the high-voltage pulses emitted from the high-voltage pulse generation circuit section to generate high voltage. a high voltage output section provided on the secondary winding of the flyback transformer to obtain a high voltage output section; and a high voltage output section provided on the secondary winding of the flyback transformer; A fifth switch connected in parallel to the second switch is connected to the intermediate connection point of the third and fourth diode series circuits connected between the switches, and is connected to the other end of the primary winding of the control transformer. between the one end of the primary winding of the control transformer and the other end of the primary winding of the flyback transformer. The output voltage of the high voltage output section is determined by comparing a sample voltage obtained by dividing the output of the high voltage output section with a reference voltage obtained by dividing the voltage of the power supply. The third switch is controlled by using a control pulse that controls the turn-on time of the third switch according to the fluctuation and a divided voltage output from the intermediate tap of the primary winding of the flyback transformer as a timing pulse. and a control circuit section that outputs a control pulse that turns off the control circuit.

[Effect]

According to the high voltage stabilizing circuit according to the present invention, the deflection current of the horizontal deflection coil is controlled by the first switch, and the high voltage DC voltage is controlled by the second and third switches. is not affected by the high voltage generation circuit and can obtain a stable raster size.

〔Example〕

FIG. 1 shows an embodiment of a high voltage stabilizing circuit according to the present invention. In addition, in FIG. 1, for convenience of explanation, the parts corresponding to the circuit shown in FIG. 4 are given the same reference numerals, and the parts corresponding to the circuit shown in FIG. Reference numerals 101 to 10 are used for each part.
5, and detailed explanation thereof will be omitted.

The high voltage stabilizing circuit shown in FIG. 1 includes a deflection circuit section 100 dedicated to deflection (corresponding to the circuit shown in FIG. 2).
A high voltage generation circuit section 200 (corresponding to the circuit shown in FIG. 4) is configured exclusively for high voltage generation. The deflection circuit section 100 uses a chiyoke coil 106 in place of the flyback transformer 6 and rectifier circuit in FIG. 2, and the high voltage generation circuit section 200 uses a chiyoke coil 201 in place of the deflection coil 5 in FIG. In addition, these deflection circuit section 100 and high voltage generation circuit section 20
The output of the horizontal drive circuit 10 is commonly applied to the bases of the transistors 101 and 1. These transistors 101 and 1 operate as first and second switches, respectively, and switch 27 is configured to operate as a third switch.

Deflection circuit section 10 of the high voltage stabilizing circuit as described above
0, as mentioned above, the choke coil 106 is used instead of the flyback transformer 6 shown in FIG. 2, so the waveform of the current flowing through the deflection coil 105 is the same as that explained in FIG. , a good deflection current waveform can be obtained.

Furthermore, regarding the high voltage generation circuit 200, the fourth
Since the deflection coil 201 is used instead of the deflection coil 5 in the figure, the waveform of the current flowing through the deflection coil 201 is the same as that explained in FIG. 4, and other parts are also the same as in FIG. Therefore, a high voltage pulse similar to the flyback pulse in FIG. 4 is applied to the high voltage transformer (flyback transformer) 6.
A control pulse similar to the control pulse in FIG. 4 is added to this high voltage pulse, and the high voltage output operation V _H of the high voltage output terminal 9 is controlled to a constant value. These operations are similar to those in FIG. 4.

Since this control pulse does not flow through the transistor 101 of the deflection circuit section 100, the raster size is not affected by the operating state of the high voltage stabilizing circuit.

[Effect of idea]

As is clear from the above-mentioned embodiments, according to the present invention, by providing the deflection circuit section independently from the high voltage generation circuit section, the raster size remains constant regardless of the operating state of high voltage stabilization. You can get good images.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a high voltage stabilizing circuit according to the present invention, Fig. 2 is a circuit diagram showing an example of a high voltage generating circuit, and Figs. FIG. 4 is a circuit diagram of a conventional high voltage stabilizing circuit. 100...Deflection circuit section, 200...High voltage generation circuit section, 1,101...Transistor, 6...High voltage transformer, 9...High voltage output terminal, 10...Horizontal drive circuit, 27...Switch, 28 ... Control circuit, 105 ... Deflection coil, 106, 201 ...
Chiyoke coil.

Claims (1)

[Claims for Utility Model Registration] A first switch that is turned on and off by the output of the horizontal drive circuit is provided between the power supply and one end of the first stationary coil, and a first switch is provided in parallel with the first switch. a deflection circuit section including a diode connected to a first capacitor, and a series circuit of a first large capacity capacitor and a horizontal deflection coil connected in parallel to the first capacitor; the power supply; and a flyback transformer. A second switch that is turned on and off by the output of the horizontal drive circuit is provided between one end of the primary winding of the control transformer and the secondary winding of the control transformer connected to one end of the primary winding of the transformer. A second diode and a second capacitor are respectively connected to the second diode and a second capacitor, and a series circuit of a second large capacitance capacitor and a second choke coil is connected in parallel to the second capacitor, and the second switch is turned on and off. a high-voltage pulse generation circuit section that accumulates power during a scanning period through off-operation and emits high-voltage pulses during a retrace period; and a high-voltage pulse generation circuit section that accumulates power during a scanning period and emits high-voltage pulses during a retrace period, and rectifies and smoothes the high-voltage pulses emitted from the high-voltage pulse generation circuit section to obtain high voltage. A high-voltage output section provided on the secondary winding of the flyback transformer, and a connection between the power supply and the other end of the primary winding of the flyback transformer at one end of the primary winding of the control transformer. A fifth and a fourth diode series circuit connected in parallel to the second switch are connected to the other end of the primary winding of the control transformer. a first end of the primary winding of the control transformer and the other end of the primary winding of the flyback transformer; By comparing the sample voltage obtained by dividing the output of the high voltage output section and the reference voltage obtained by dividing the voltage of the power supply with the switch No. 3, fluctuations in the output voltage of the high voltage output section are detected. Accordingly, the third switch is turned off using a control pulse that controls the turn-on time of the third switch and a divided voltage output from the intermediate tap of the primary winding of the flyback transformer as a timing pulse. 1. A high voltage stabilizing circuit comprising: a control circuit section that outputs a control pulse to make the output of the high voltage stabilizer;