JP2596943B2 - Horizontal deflection circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a horizontal deflection circuit, and more particularly to a horizontal deflection circuit in which a horizontal oscillation circuit oscillates stably and quickly when power is turned on.

[Prior Art] Recently, a horizontal oscillation circuit has been proposed in which a current signal is input as an oscillation control signal to control the oscillation frequency. The circuit shown in FIG. 5 controls the oscillation of such a horizontal oscillation circuit. A signal (current signal) is formed.

In FIG. 5, the horizontal / synchronous signal HD is converted into a voltage signal V1 corresponding to the horizontal / synchronous frequency in the frequency / voltage conversion circuit 1 and supplied to the limiter circuit 2. Limiter circuit 2
Gives the voltage signal V1 to the voltage / current conversion circuit 3 with the upper and lower limits in consideration of the dynamic range of the subsequent circuit.

Thus, the voltage / current conversion circuit 3 converts the current signal I within the dynamic range into a current signal I proportional to the voltage signal V2, which is supplied to the horizontal oscillation circuit 4 as an oscillation control signal to control the oscillation frequency of the horizontal oscillation signal OSC. Has been made.

[Problems to be Solved by the Invention] By the way, when the power is turned on, the voltage is not converted by the frequency / voltage conversion circuit 1, so that the horizontal oscillation circuit 4 does not oscillate as it is. Therefore,
When the power is turned on, the lower limit value of the limiter circuit 2 may be supplied to the horizontal oscillation circuit 4 via the voltage / current conversion circuit 3 to perform the oscillation operation.

However, as shown by the broken line in FIG. 3, the limiter circuit 2 controls the lower limit value VL with respect to the fluctuation of the power supply voltage Vcc.
Is changed in proportion to allow stable operation even when the voltage is reduced, so the lower limit value VL is small at low voltage when the power is turned on, and it cannot be used in practice, but it can be used after it has been increased to some extent. , The rise of the horizontal oscillation operation is delayed.

In this case, the power supply voltage Vcc
As the value rises, the lower limit value VL also rises, and oscillates soon. At this time, as shown by the broken line in FIG. 4, the frequency rises from a small frequency to a predetermined horizontal oscillation frequency. However, in order to protect the deflection stage of the horizontal deflection circuit, it is generally desirable to change the frequency from a high frequency to a predetermined horizontal oscillation frequency when the power is turned on. In this respect, the conventional circuit is insufficient. is there.

The present invention has been made in consideration of the above points, and oscillates from a lower power supply voltage at the time of turning on the power to accelerate the rise of the oscillating operation, and raises the frequency from a high frequency to a predetermined horizontal oscillation frequency. It is an object of the present invention to provide a horizontal deflection circuit capable of protecting a deflection stage.

[Means for Solving the Problems] In order to solve such problems, the present invention provides a frequency / voltage conversion circuit that receives a horizontal synchronization signal and obtains a voltage signal according to the horizontal synchronization frequency, The voltage signal from the voltage conversion circuit is limited to a predetermined range. In addition, a limiter circuit in which at least the lower limit value changes in proportion to the power supply voltage, a voltage / current conversion circuit that converts a voltage signal from the limiter circuit into a current signal, and a horizontal oscillation circuit that oscillates based on the current signal In a horizontal deflection circuit having a
In addition, an auxiliary voltage supply circuit that supplies an auxiliary voltage to the limiter circuit that gradually approaches the lower limit value proportional to the power supply voltage with the increase of the power supply voltage is provided, and the limiter circuit is provided in a range where the power supply voltage immediately after power-on is small. The auxiliary voltage is set to the lower limit of the limit.

[Operation] Since the voltage signal is not output from the frequency / voltage conversion circuit immediately after the power is turned on, the horizontal oscillation operation is performed with the lower limit value of the limit as the output of the limiter circuit.

At this time, the limiter circuit does not use the lower limit value obtained in proportion to the power supply voltage but a larger auxiliary voltage from the auxiliary voltage supply circuit as the lower limit value in a small range of the power supply voltage. The horizontal oscillation operation can be started up quickly.

In addition, the auxiliary voltage is relatively increased as the power supply voltage is smaller than the lower limit lower limit obtained in proportion to the power supply voltage, and is gradually matched, so that the horizontal oscillation frequency is changed from a high frequency to a low frequency. Thus, the horizontal deflection circuit can be started up by changing it so that the deflection stage of the horizontal deflection circuit can be protected.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1 in which the same reference numerals are given to corresponding parts in FIG. 5, this embodiment includes an auxiliary voltage supply circuit 10 for supplying an auxiliary voltage to the limiter circuit 2 when power is turned on.

The auxiliary voltage supply circuit 10 is formed in detail with a configuration as shown in FIG. In FIG. 2, a resistor R1 and a Zener diode ZD are sequentially connected in series between a power supply line L1 and an earth line L2, and the connection point is connected to the base of an NPN transistor Q1. The collector of the transistor Q1 is connected to the power supply line L1, and the emitter of the transistor Q1 is connected to the ground line L2 via the resistor R2 and three NPN transistors Q2 to Q4 which are diode-connected in sequence.

Furthermore, the connection point between the resistor R2 and the transistor Q2 is PNP
It is connected to the base of the type transistor Q5. The emitter of the transistor Q5 is connected to the power supply line L1 via the resistor R3, and the collector of the transistor Q5 is connected to the ground line L2. The emitter of transistor Q5 is also NPN
It is connected to the base of the type transistor Q6. The collector of the transistor Q6 is connected to the power supply line L1, and the emitter is connected to the limiter lower limit value line (not shown) of the limiter circuit 2.

The limiter lower limit line is normally set to a voltage obtained by dividing the power supply voltage Vcc by a predetermined ratio, but when the emitter voltage of the transistor Q6 is large, the limiter lower line is set to take this emitter voltage. I have.

Note that, due to the above connection, the emitter voltage (auxiliary voltage) of the transistor Q6 is substantially equal to the base voltage VB (Q5) of the transistor Q5.

In the above configuration, when the power is turned on, the power supply voltage
Vcc gradually increases toward a regular voltage (for example, 12 [V]). Here, in a state where the power supply voltage Vcc is small and the Zener diode ZD is cut off (for example, the breakdown voltage of the Zener diode ZD is 5.6 [V]),
The emitter voltage VE (Q1) of the transistor Q1 is expressed by the following equation: VE (Q1) = Vcc−VBE (Q1) −R1 × IB (Q1) ≒ Vcc−VBE (Q1) (1) (where VBE (Q1) Is the base-emitter voltage of the transistor Q1, and IB (Q1) is the base current of the transistor Q1). When the emitter voltage VE (Q1) is low, the transistors Q2 to Q4 are cut off, and the base voltage VB (Q1) of the transistor Q5, that is, the output voltage of the auxiliary voltage supply circuit 10, is expressed by the following equation: VB (Q5) = VE (Q1) ≒ Vcc−VBE (Q1) (2) The slope portion of the solid curve in FIG. 3 corresponds to this.

As the power supply voltage Vcc rises, the emitter voltage VE (Q1) of the transistor Q1 also rises, and when the transistors Q2 to Q4 rise, the base voltage VB (Q5) of the transistor Q5
Is given by the following equation: VB (Q5) = VBE (Q2) + VBE (Q3) + VBE (Q4) = 3 × VBE (3) (where VBE (Q2), VBE (Q3) and VBE (Q4) are respectively (Base-emitter voltage of transistors Q2, Q3, Q4) as shown in (2), the sum of the base-emitter voltages of transistors Q2 to Q4.

Furthermore, the power supply voltage Vcc rises and the Zener diode Z
Even if D rises, since the transistors Q2 to Q4 are rising, the base voltage VB (Q5) of the transistor Q5
Is as shown in equation (3).

Therefore, the base voltage VB (Q5) of the transistor Q5 is
In other words, the auxiliary voltage by the auxiliary voltage supply circuit 10 gradually increases with respect to the power supply voltage Vcc until the transistors Q2 to Q4 rise, as shown by the solid line in FIG. 3, and the transistors Q2 to Q4 rise. When the voltage becomes higher than the power supply voltage, it takes a substantially constant value (3V BE).

On the other hand, in the limiter circuit 2, the power supply voltage Vcc
Lower limit value VL obtained by dividing the pressure by a predetermined ratio α
Changes in proportion to the power supply voltage Vcc as shown in the following equation: VL = αVcc (4) The broken line curve in FIG. 2 corresponds to this.

The limiter circuit 2 supplies the auxiliary voltage VB (Q5) to the voltage / current conversion circuit 3 as the lower limit value of the auxiliary voltage VB (Q5) in a range larger than the lower limit value VL obtained by dividing the auxiliary voltage VB (Q5). In the range where Q5) is smaller than the lower limit value VL obtained by voltage division, the lower limit value VL obtained by voltage division is given to the voltage / current conversion circuit 3 as the lower limit value. In practice, since the partial pressure ratio α is selected to be about 0.3, the switching of the output lower limit value is performed at about 7 [V] as a boundary.

Here, in the range in which the auxiliary voltage VB (Q5) is selected by the limiter circuit 2, the ratio of the lower limit value to the power supply voltage Vcc is larger than the regular ratio α, and the lower the power supply voltage Vcc, the larger the ratio. Therefore, the voltage / current conversion circuit 3 supplies a relatively large and declining current signal I to the horizontal oscillation circuit 4, so that the horizontal oscillation circuit 4 starts from a high frequency as shown in the first half of the solid line in FIG. The horizontal oscillation signal OSC that gradually decreases is output.

Further, in the range where the lower limit value VL obtained by the voltage division is selected by the limiter circuit 2, the ratio of the lower limit value to the power supply voltage Vcc is the normal ratio α. Numeral 3 gives a relatively flat current signal I to the horizontal oscillation circuit 4, so that the horizontal oscillation circuit 4 outputs a horizontal oscillation signal OSC having a constant frequency as shown by the latter half of the solid line in FIG.

In this manner, until the power supply voltage Vcc becomes the normal voltage value, the oscillation operation is performed according to the voltage signal based on the auxiliary voltage VB (Q5) or the lower limit value VL obtained by dividing the voltage,
After the voltage value becomes a regular voltage value, the oscillation operation is performed according to the voltage signal V1 converted by the frequency / voltage conversion circuit 1.

Therefore, according to the above-described embodiment, in the small range of the power supply voltage Vcc at the time of turning on the power, the voltage / current conversion is performed using the auxiliary voltage relatively larger than the power supply voltage Vcc from the auxiliary voltage supply circuit 10 as the lower limit limit. Since the horizontal oscillation circuit 4 is supplied to the horizontal oscillation circuit 4 via the circuit 3, the oscillation operation can be performed from a small range of the power supply voltage Vcc, the start-up of the oscillation operation can be accelerated, and the frequency can be changed from a high frequency to a low frequency. The horizontal oscillation frequency can be changed, and the deflection stage of the horizontal deflection circuit can be protected.

The auxiliary voltage supply circuit 10 according to the present invention is not limited to the one having the detailed configuration shown in FIG. 2, but may have any configuration as long as it can realize the change shown by the solid line in FIG. good.

[Effects of the Invention] As described above, according to the present invention, in a range where the power supply voltage immediately after turning on the power is small, the power supply voltage is larger than the lower limit lower limit obtained by dividing the power supply voltage from the auxiliary voltage supply circuit to the limiter circuit. In addition, since the auxiliary voltage that gradually approaches the lower limit of the divided voltage is given to the lower limit of the limiter, the rise of the horizontal oscillation circuit that oscillates based on the lower limit of the power supply voltage in a range where the power supply voltage is small is increased. And a horizontal deflection circuit capable of protecting the deflection stage by raising the horizontal oscillation frequency from a high frequency to a low frequency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a horizontal deflection circuit according to the present invention, FIG. 2 is a connection diagram showing a detailed configuration of the auxiliary voltage supply circuit, and FIG. FIG. 4 is a characteristic curve diagram showing a relationship between a lower limit value and a limit, FIG. 4 is a characteristic curve diagram showing a relationship between a power supply voltage and a horizontal oscillation frequency, and FIG. 5 is a block diagram showing a conventional circuit. 1 ... frequency / voltage conversion circuit, 2 ... limiter circuit, 3
…… voltage / current conversion circuit, 4 …… horizontal deflection circuit, 10 ……
Auxiliary voltage supply circuit.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-130072 (JP, A) JP-A-64-16075 (JP, A)

Claims (1)

(57) [Claims] A frequency / voltage conversion circuit for inputting a horizontal synchronization signal to obtain a voltage signal corresponding to a horizontal synchronization frequency, and the voltage signal from the frequency / voltage conversion circuit is limited to a predetermined range. In addition, a limiter circuit in which at least the lower limit value changes in proportion to the power supply voltage, a voltage / current conversion circuit that converts a voltage signal from the limiter circuit into a current signal, and a horizontal oscillation circuit that oscillates based on the current signal In the horizontal deflection circuit provided, in a range where the power supply voltage immediately after turning on the power is small, the power supply voltage is larger than the lower limit value proportional to the power supply voltage, and
An auxiliary voltage supply circuit for supplying an auxiliary voltage to the limiter circuit, which gradually approaches the lower limit value in proportion to the power supply voltage with an increase in the power supply voltage, wherein the limiter circuit is connected to the power supply voltage immediately after power-on. A horizontal deflection circuit, wherein the auxiliary voltage is set to a lower limit of the limit in a range where is smaller.