KR900003644Y1 - Automatic control apparatus for discharge lamps - Google Patents

Abstract

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Description

TV's horizontal oscillation circuit

1 is a block diagram showing a conventional horizontal oscillation circuit.

2 is an implementation circuit diagram of the present invention.

3a and b are voltage waveform diagrams for explaining the operation of the present invention.

* Explanation of symbols for main parts of the drawings

31, 37: first and second time constant circuit section 32, 36: first and second differential amplifier section

33, 39: first and second switching unit 34, 38: first and second waveform shaping unit

35: voltage converter C ₁ , C ₂ : capacitor

R ₁ -R ₁₂ : Resistor Q ₁ -Q ₁₃ : Transistor

The present invention relates to a circuit that can prevent abnormal oscillation phenomenon in the horizontal oscillation circuit of TV.

In a television receiver, the frequency of a predetermined oscillator circuit in the receiver is controlled to obtain an image caught on a received broadcast signal on the receiving tube, thereby obtaining synchronization with the broadcast signal.

That is, a circuit which needs to be synchronized with a broadcast signal received in a horizontal oscillation circuit or a vertical oscillation circuit, is synchronized with the reception broadcast using an automatic frequency control (AFC) circuit.

FIG. 1 is a block diagram of a conventional horizontal oscillation circuit that obtains synchronization by such an AFC circuit. In the synchronization circuit 1, phase detection and control are performed by separating the synchronization signal S ₁ from an input composite video signal. It supplies to the AFC circuit 2 which is a circuit. In this AFC circuit, phase detection is performed by phase-detecting a sawtooth signal obtained by integrating the synchronization signal S ₁ input from the synchronization separation circuit 1 and the flyback pulse S ₂ supplied from the flyback transformer 5. The oscillation frequency of the horizontal oscillation circuit 3 is controlled by supplying a voltage to the horizontal oscillation circuit 3, and the output signal oscillated in the horizontal oscillation circuit 3 is supplied to the horizontal oscillation circuit 4, thereby providing a flyback transformer. The primary winding L ₁ of (5) is driven.

At this time, the secondary winding L ₂ of the flyback pulse 5 is connected to the automatic beam adjustment (ABL) circuit and the high voltage diode (D _HV ), and the flyback pulse ( ₃ ) described above in the tertiary winding (L ₃ ). S ₂ ) is obtained.

Accordingly, the horizontal oscillation circuit 3 outputs an oscillation frequency synchronized with the reception broadcast signal by controlling the oscillation frequency by the AFC voltage. If there is no reception broadcast signal, the horizontal oscillation circuit 3 performs this circuit. The oscillation is caused by the frequency determined by the integer of.

However, in this case, in the high voltage circuit or the horizontal output circuit 4, for example, a switching splius (i.e., a high voltage diode (D _HV ) or a damping diode connected to the flyback transformer 5) synchronized with the magnetic oscillation frequency Is generated during the switching operation, etc.), whereby the switching pliers fly into the front end of the antenna or the intermediate frequency amplification circuit and are generated as homologous signals and then separated as a synchronous signal in the synchronous separation circuit (1). As a result, when the switching splits fly to the front end of the antenna or the intermediate frequency amplifier circuit, a frequency close to the synchronization signal is generated. Furthermore, the synchronization frequency due to the switching split is designed to be placed at the entrance of the intermediate frequency amplifier circuit. Phase delay occurs while passing through a saw filter, etc., and is detected and separated as a pseudo synchronous signal of phase.

Therefore, when the ground motor signal is input to the AFC circuit 2, the oscillation frequency of the horizontal oscillation circuit 3 is controlled to be lower, so that the oscillation frequency of the horizontal oscillation circuit 3 moves to an extremely low frequency in an instant. As a result, an abnormal voltage is generated in the flyback transformer 5, or a malfunction occurs in the high voltage protection circuit.

An object of the present invention is to solve the abnormal oscillation phenomenon of the horizontal oscillation circuit, the second oscillation circuit having a predetermined oscillation frequency lower than the oscillation frequency of the first oscillation circuit in the first oscillation circuit having a predetermined oscillation frequency When the oscillation is performed by the first oscillation circuit in normal operation and the oscillation frequency of the first oscillation circuit is not lower than the oscillation frequency of the second oscillation circuit during abnormal oscillation, the extreme oscillation frequency is lowered. It is designed to prevent the abnormal voltage generation or malfunction of the high-voltage circuit portion due to the flyback transformer, the configuration and operation effects of the present invention will be described in detail by the accompanying drawings.

The output terminals of the first time constant circuit part 31 including the resistors R ₇ (R ₈ ) and the capacitor C ₁ to which the Vcc voltage and the AFC voltage are input are connected to the transistors Q ₁ (Q ₂ ) and the resistors R _1. ) (R _2), the first connected to the differential amplifier section (the first switching unit (33 a to connect the inverting input terminal, and at the same time the resistance (R ₃₎ (R ₄₎ and a transistor (Q ₇₎ of the 32)) in the The output terminal of the first differential amplifier 32 is connected to the input terminal of the first waveform shaping section 34 of the transistors Q ₃ and Q ₆ , and the first waveform shaping section 34 is connected to the input terminal of the first waveform shaping section 34. The output terminal (a) is connected to a normal horizontal output circuit (4), and the second output terminal (b) is connected to the input terminal of the first switching unit 33, the resistors R ₅ (R ₆ ), and the transistor Q. ₈ ) is grounded to the input terminal of the voltage changing section 35 and grounded through a resistor R ₉ , and the output terminal of the voltage converting section 35 is non-inverted by the first differential amplifier 32. A first oscillation circuit is formed by connecting to an input terminal, and the first differential amplifier 32 Connects the input terminal of the second differential amplifier 36 of the transistor Q ₁₂ to the common gate to the second switching unit 39 of resistor R ₁₀ (R ₁₁ ) and transistor Q ₁₃ . At the same time as the output terminal of the second time constant circuit portion 37 consisting of a resistor R ₁₂ and a capacitor C ₂ having a larger time constant than the first time constant circuit portion 31, and The output terminal of 36 is connected to the input terminal of the second waveform shaping section 38 of the transistors Q ₉ -Q ₁₁ , and the output terminal of the second waveform shaping section 38 and the second switching section 39 above. A second oscillation circuit is constructed by coupling the input terminal of the terminal to the second output terminal b of the first waveform shaping section 34.

In the description, I ₀ is a current source and 2 is an AFC circuit.

The circuit operation state of the present invention configured as described above is as follows.

First, in the steady state with the reception broadcast input, the capacitor C _{1 in} the first time constant circuit 31 is supplied with the resistor R ₈ and the Vcc voltage to which the AFC voltage from the AFC circuit 2 is applied. The charging voltage is supplied to the base of the transistor Q _{2 in} the first differential amplifier 32 while gradually charging by the time constant combination with the resistor R ₇ .

This charging voltage is the base voltage of the transistor Q _{1 in} the first differential amplifier 32. When it reaches, the transistor Q ₂ is turned on, so that each transistor Q ₃ -Q _{6 in} the first waveform shape section 34 is turned on, so that the first output terminal a of the first waveform shape section 34 is connected. And the oscillation frequency is output to the second output terminal (b), whereby a current flows through the resistor (R ₉ ) connected to the collector of the transistor (Q ₅ ) to generate a control voltage across the resistor (R ₉ ). As a result, the first and second switching units 33 and 39 and the transistors Q ₇ and Q ₁₃ and Q _{8 in the} voltage changing unit 35 are both turned on.

Thus, the charge charged in the capacitor C ₁ is discharged through the resistor R ₃ and the transistor Q _{7 in} the first switching unit 33, and at the same time, the charge of the transistor Q _{8 in the} voltage conversion unit 35 is discharged. By conduction, the resistor R ₆ is connected in parallel to the resistor R _{2 in} the first differential amplifier 32 so that the base voltage of the transistor Q ₁ is lowered.

That is, the base voltage of this transistor Q ₁ is the voltage It is determined to a value, wherein the capacitor (C ₁₎ when the discharge, while the base voltage of the transistor (Q ₂₎ reaches the base voltage (V _L) of the transistor, the transistor (Q ₂₎ is conductive.

As a result, all of the transistors Q ₃ -Q _{6 in} the first waveform shaping section 34 are 'off', and control voltages are not generated at both ends of the resistor R ₉ , so that each transistor Q ₇ (Q ₁₃ ). (Q ₈ ) Also all are 'off' so the capacitor (C ₁ ) will post a charge again.

On the other hand, the capacitor C _{2 in} the second time constant circuit portion 37 is also at the same timing as the first time constant circuit portion 31 by the same 'on / off' operation of the transistors Q ₇ and Q ₁₃ . In the normal state in which the broadcast signal is received as described above, the point A is supplied with an AFC voltage for synchronizing with the frequency of the received broadcast signal from the AFC circuit 2 and is overlapped. As described above, since the signal waveform voltage at point A is higher than the signal waveform voltage at point B, and the time constant of the second time constant circuit portion 37 is set slightly larger than the first time constant circuit portion 31, the second differential amplifier portion 36, transistors in the (Q ₁₂₎ of the second oscillator circuit being maintained in "off" state is let no effect on the oscillation frequency of the first oscillator circuit.

Secondly, in the case of no oscillation frequency and the oscillation frequency of the oscillation circuit and the abnormal oscillation state which are extremely lowered as described above, the AFC voltage supplied from the AFC circuit 2 is lowered. transistor (Q ₂₎ in the watch so that the point B signal waveform voltage is more quickly reached the base voltage (V _H) of the transistor (Q ₁₎ than the signal wave voltage of the point a as a first differential amplifying section 32 ''Off' and transistor Q _{12 in} second differential amplifier 36 is turned on.

Accordingly, the control voltage is generated at both ends of the resistor R ₉ by the current flowing through the collector of the transistor Q ₁₁ , which is the output terminal of the second waveform shaping portion 38, thereby providing a transistor Q ₇ (Q ₁₃ ) ( Q ₈ ) is conducted.

In this case, therefore, the oscillation output of the first oscillation circuit is set by the oscillation frequency of the second oscillation circuit set by the time constants of the resistor R ₁ 2 and the capacitor C ₂ in the second time constant circuit portion 37. Since the oscillation frequency of the second oscillation circuit is set slightly lower than the normal oscillation frequency of the first oscillation circuit because it is regulated, the oscillation frequency of the first oscillation circuit does not become lower than the oscillation frequency of the second oscillation circuit, thereby making the extreme Abnormal rash can be prevented.

The present invention as described above can prevent abnormal oscillation when the oscillation frequency of the horizontal oscillation circuit is extremely low when it is not received between broadcast signals, thereby eliminating abnormal voltage generation or malfunction of the high voltage protection circuit. It is a useful design.

Claims (1)

The output terminals of the first time constant circuit part 31 including the resistors R ₇ (R ₈ ) and the capacitor C ₁ to which the Vcc voltage and the AFC voltage are input are connected to the transistors Q ₁ (Q ₂ ) and the resistors R _1. ) (R _2), the first connected to the differential amplifier section (the first switching unit (33 a to connect the inverting input terminal, and at the same time the resistance (R ₃₎ (R ₄₎ and a transistor (Q ₇₎ of the 32)) in the The output terminal of the first differential amplifier 32 is connected to the input terminal of the first waveform shaping unit 34 of transistors Q ₃ -Q ₆ , and the first output stage of the first waveform shaping unit 34. (a) is connected to a normal horizontal output circuit (4), and its second output terminal (b) is connected to the input terminal of the first switching unit 33, resistors R ₅ (R ₆ ) and transistors Q ₈ And grounded through the resistor (R ₉ ) at the same time as the input terminal of the voltage conversion unit (35), and the output terminal of the voltage conversion unit (35) is the non-inverting input terminal of the first differential amplifier (32). A first oscillation circuit connected to the first differential amplifier 32, Emitter is connected to the input terminal of the second differential amplifier unit 36 to the gongjeop the transistor (Q ₁₂₎ to the resistor (R ₁₀₎ (R ₁₁₎ and a transistor (Q _13), a second switching unit 39 to the box and At the same time, the second differential amplifier unit is connected to the output terminal of the second time constant circuit unit 37 having a resistor R ₁₂ and a capacitor C ₂ having a larger time constant than the first time constant circuit unit 31. An output terminal of (36) is connected to an input terminal of the second waveform shaping section 38 of the transistors Q ₉ -Q ₁₁ , and the output terminal of the second waveform shaping section 38 and the second switching section 39 of the current pull are 39. TV's horizontal oscillation circuit comprising a second oscillation circuit by making a second oscillation circuit in common with the second output terminal (b) of the first waveform shaping portion (34).