JP3330806B2 - Sound fluctuation prevention circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an audio output voltage and + B
Line voltage to the same switching mode transformer
In the power supply circuit supplied on the secondary side of the transformer (hereinafter referred to as a transformer), when the audio output fluctuates, the audio output + B line voltage fluctuates, and + B1
The present invention relates to a sound fluctuation prevention circuit for preventing a change in screen amplitude caused by a change in output voltage.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional sound fluctuation preventing circuit of a television receiver in which an audio output voltage and a + B line voltage are supplied by the same transformer. Although the primary side of the transformer 1 is omitted from this sound fluctuation prevention circuit, the circuit 1
The + B1 voltage output terminal 2 on the next side is connected to the anode of the rectifying diode 6, the cathode of which is connected to one end of the smoothing capacitor 8, and the other end is grounded. The + B2 audio voltage output terminal 3 on the secondary side of the transformer 1 is connected to the anode of a rectifying diode 7, the cathode of which is connected to one end of a smoothing capacitor 9 and the other end is grounded. I have. The cathode of the rectifying diode 7 is connected to a voice load circuit 31. The rectifying diode 6
Is connected to one end of a resistor 10 for + B adjustment and high-voltage regulation correction for a flyback transformer (FBT) 11, and the other end of the resistor 10 is connected to a terminal 11 a of the FBT 11.
It is connected to the. The other terminal 11b of the FBT 11 is connected to the collector of the horizontal output transistor 12.

A diode modulator circuit is a diode
The horizontal output transistor 12 has a collector connected to the cathode of the diode 13, and an anode connected to the cathode of the diode 14. I have. The anode of the diode 14 is grounded. Capacitor 15 is connected in parallel with diode 13, and capacitor 16 is connected in parallel with diode 14. Further, a connection point between the anode of the diode 13 and the cathode of the diode 14 is connected to one end of a coil 18, the other end of the coil 18 is connected to one end of a capacitor 17, and the other end of the capacitor 17 is grounded.

The intersection of coil 18 and capacitor 17 is also connected to the collectors of Darlington-connected transistors 22 and 23, the emitter of transistor 23 being grounded,
The base of the transistor 23 is connected to the emitter of the transistor 22 and the resistor 26, and the other end of the resistor 26 is grounded. The base of the transistor 22 is connected to the base current pulling resistor 25 and the collector of the transistor 19,
The other end of the resistor 25 is grounded.

The emitter of the transistor 19 is connected to a resistor 27 and a pinion (EW) input signal line 30,
The other end of 27 is connected to + B DC power supply 24, and a transistor
The base of 19 is connected to base bias resistors 20 and 21, the other end of resistor 20 is grounded, and the other end of resistor 21 is connected to + B DC power supply 24.

In the sound fluctuation preventing circuit of this television receiver, the + B1 voltage output terminal 2 supplies the + B1 output voltage to the terminal 11a of the FBT 11, and the + B2 audio voltage output terminal 3 supplies the audio to the audio load circuit 31. An output + B line voltage is supplied, and a pinching (EW) input signal is input to the emitter of the transistor 19 from a pinching (EW) input signal line 30 for adjusting the screen amplitude.
The signal is input to the terminal 11b of the FBT 11 via the element 23 and the elements 13 to 18 of the diode modulator circuit.

[0007]

However, in the configuration of the sound fluctuation prevention circuit of FIG. 2, when the sound output fluctuates, the + B2 sound voltage output terminal 3 to the sound load circuit 31 is output.
The audio output + B line voltage supplied from the FB also fluctuates. As a result, the + B1 output voltage from the + B1 voltage output terminal 2 on the same secondary side as the transformer 1 also fluctuates, and this interlocks with the screen amplitude, and the image receiving screen of the television receiver fluctuates.
(Sound shaking).

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the problem of the sound fluctuation on the image receiving screen by a simple means.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems
In addition, the sound fluctuation prevention circuit of the present invention supplies the sound to the sound output circuit.
Primary DC voltage and primary winding of flyback transformer
The second DC voltage supplied to one end of the
A power supply circuit supplied from the secondary side and the flyback transformer.
Diode module connected to the other end of the primary winding of the
Data circuit and the diode modulator circuit.
Pink that supplies a pincushion signal to one end of the coil
Input signal signal and the pin cushion signal circuit.
Transistors that amplify the input pincushion input signal
And the diode modulator circuit.
And a capacitor inserted between the other end of the coil
And a series connection circuit with a resistor.
When the first DC voltage fluctuates, the series connection circuit
The amount of change in the second DC voltage is
Supply the input signal to the base of the amplifying transistor.
Thereby forming the diode modulator circuit.
At the other end of the coil to change the amount of change in the second DC voltage.
Configure a negative feedback circuit to perform negative feedback, and
This is to prevent screen amplitude fluctuation .

According to the present invention, the audio output fluctuates and the audio supplied from the + B2 audio voltage output terminal 3 only by adding a simple negative feedback circuit composed of a voltage feedback capacitor and a current limiting resistor. The fluctuation of the + B1 output voltage supplied from the + B1 voltage output terminal 2 due to the fluctuation of the output + B line voltage is converted into a pinch (E)
W) By applying a negative feedback to the transistor which is an amplifier of the input signal, the amplitude is reduced when the audio output + B line voltage is increased, and the amplitude is increased when the audio output + B line voltage is decreased. It is to be corrected.

[0011]

Embodiments of the present invention will be described below with reference to FIG.

(Embodiment) FIG. 1 is a circuit diagram of a sound fluctuation preventing circuit according to an embodiment of the present invention. 1, circuit elements and the like having the same functions as in FIG. 2 of the conventional example are denoted by the same reference numerals, and description thereof will be omitted. 2 is that the + B1 output line on the secondary side of the transformer 1 and the FBT11
A connection point a between the diodes 13 and 14 and the coil 18 constituting the diode modulator circuit connected through the IGBT, and the base of the transistor 19 to which the pinch (EW) input signal is input and the base bias resistors 20 and 21 A negative feedback circuit of a voltage feedback capacitor 28 and a current limiting resistor 29 connected in series is connected between the connection point b and a transistor 19 which constitutes an amplifier for a pinching (EW) input signal.
Negative feedback is applied to.

The operation of the sound fluctuation preventing circuit configured as described above will be described. When the audio output increases (or decreases) in the audio load circuit 31, the + B2 output voltage of the + B2 audio voltage output terminal 3 on the secondary side of the transformer 1 decreases (or increases). Due to the influence, 2 of transformer 1
The + B1 output voltage of the + B1 voltage output terminal 2 on the secondary side is large.
(Or smaller). Further, due to the effect of the + B1 output voltage, the + B1 output voltage input to the terminal 11a of the FBT 11 increases (or decreases), and as a result, the CRT
The high pressure supplied to (not shown) becomes high (or low), and the screen amplitude becomes narrow (wide).

Therefore, by connecting a negative feedback circuit including a voltage feedback capacitor 28 and a current limiting resistor 29 between the + B1 output voltage line and the base of the transistor 19, a + B1 voltage output terminal on the secondary side of the transformer 1 is provided. When the + B1 output voltage of No. 2 increases (or decreases), the amount of the change is applied to the base of the transistor 19. Transistor
The base DC potential of 19 rises (or falls), and the base DC potential of transistor 22 also rises (or falls).

As a result, the DC potential of the collector of the transistor 23 connected in Darlington rises (or falls). And diodes 13, 14 and capacitors 15, 16
The screen amplitude is widened (or narrowed) to increase (or decrease) the midpoint potential of the diode modulator circuit composed of the following elements.Inverse correction when the voltage feedback capacitor 28 and current limiting resistor 29 are not connected Is applied to prevent sound fluctuation.

The configuration of the sound fluctuation preventing circuit may be a configuration other than the above embodiment as long as it has a function of performing a reverse correction of the screen amplitude fluctuation.

[0017]

As described above, according to the present invention, by connecting a simple negative feedback circuit consisting of a capacitor and a resistor,
When the audio output fluctuates, the fluctuation of the screen amplitude can be suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a sound fluctuation prevention circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional sound fluctuation prevention circuit.

[Explanation of symbols]

1 switching mode transformer, 2 + B1 voltage output terminal on the secondary side of switching mode transformer, 3 + B2 audio voltage output terminal on the secondary side of switching mode transformer, 11 FBT (flyback transformer) ), 12 ... horizontal output transistor, 28 ... capacitor for voltage feedback, 29 ... resistor for current limiting, 30 ... pinion (EW) input signal line.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/50-5/63 H04N 3/16-3/40

Claims (1)

(57) [Claims] 1. A first DC voltage supplied to an audio output circuit
And one end of the primary winding of the flyback transformer
Supplying a second DC voltage from the secondary side of the same transformer
A power supply circuit and a primary winding of the flyback transformer;
A diode modulator circuit connected to the other end;
At one end of the coil that constitutes the diode modulator circuit
Pin cushion signal circuit that supplies pin cushion signals
And the pink input to the pin cushion signal circuit.
The base of the transistor that amplifies the input signal
The other end of the coil that constitutes the diode modulator circuit
The series connection of a capacitor and a resistor
And a first DC voltage based on the fluctuation of the audio output.
Is changed, the second direct current is connected by the series connection circuit.
Increase the amount of voltage change by increasing the pincushion input signal.
By supplying to the base of the transistor to be widened,
The other end of the coil constituting the diode modulator circuit
Negative feedback to negatively feedback the amount of change in the second DC voltage
Configure a circuit to prevent screen amplitude fluctuations due to audio output fluctuations.
A sound fluctuation prevention circuit characterized by stopping .