JPS5846599Y2 - horizontal deflection circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a horizontal deflection circuit for television receivers, etc.
In particular, the present invention relates to a horizontal deflection circuit having a horizontal width adjustment function suitable for a horizontal frequency switching type television receiver or a television receiver called a zoom television.

In general, the horizontal frequency of television signals differs depending on the system in each country. For example, in France, the horizontal frequency of VHF is 15
．． 625 KHz (625 horizontal scanning lines), UH
In the case of F, it is 20.475 KHz (819 lines).

A television receiver has already been proposed in which a single horizontal deflection circuit can be used to receive television signals having different horizontal frequencies.

By the way, in a general horizontal deflection circuit, the amplitude of the deflection current is
It is well known that y is given by the inductance Ly of the deflection coil, the time width Ts of the horizontal scanning period, and the operating power supply voltage Vcc.

Therefore, when the horizontal frequency is switched in the horizontal frequency switching type television receiver as described above, the horizontal scanning period width Ts naturally changes, so as long as the power supply voltage Vcc is constant, the deflection current amplitude IY In other words, the horizontal width of the screen changes.

Therefore, in such a television receiver, in order to prevent the horizontal width from changing even when the horizontal frequency is changed, it is necessary to change the operating power supply voltage of the horizontal deflection circuit according to the change in the horizontal frequency, for example, as shown in Figure 1. Alternatively, as shown in FIG. 2, the horizontal width adjustment coil was moved closer and closer to each other.

However, in the method shown in Figure 1, two types of power supplies (high and low) (+
VCC1) (+vCC2) must be prepared. Moreover, at that time, a fairly large current flows through the horizontal deflection circuit, so if the lower voltage of the two types of power supplies is divided by a resistor, the divided voltage The drawback was that the power loss in the resistor could not be ignored.

In addition, with the method shown in Figure 2, in order to increase the amount of horizontal width adjustment, it is necessary to increase the number of turns of the width adjustment coil and increase the inductance. The resonant frequency determined by the correction capacitor and the deflection coil changes greatly, distorting the waveform of the horizontal deflection current, and furthermore,
At that time, the power supply voltage (
+Vcc) had to be set large in advance.

In addition, such adjustment or change of the horizontal width is not only for horizontal frequency switching type television receivers as mentioned above, but also for correction when the horizontal width slightly changes due to some reason in ordinary television receivers. It is also necessary when a part of the screen is enlarged with a receiver called a zoom television, and the same thing as described above can be said in such cases as well.

Therefore, the present invention was developed with these points in mind, and proposes a horizontal deflection circuit that allows for efficient and easy adjustment and change of the horizontal width.The details of the circuit will be explained below. .

FIG. 3 shows an embodiment of the horizontal deflection circuit of the present invention, in which 1 is a horizontal output transistor, 2 is a damper diode, 3 is a resonant capacitor, 4 is a horizontal deflection coil, and 5 is a three-figure correction capacitor.

6 is a flyback transformer comprising a primary winding 7 and a secondary winding 8, which further includes a tertiary winding 9 for horizontal width adjustment.
One end of this tertiary winding is grounded, and the other end is connected to one fixed terminal a of the changeover switch 10.

The other fixed terminal of the changeover switch 10 is grounded, and the movable terminal C is connected to the three-character correction capacitor 5.

In the embodiment shown in FIG. 3, the selector switch 10 is
When switched to the side, the circuit operates like a conventional horizontal deflection circuit, with the horizontal deflection coil 4
There is a relationship between the amplitude Vcp of the primary flyback pulse applied to the primary flyback pulse and the amplitude Iy of the horizontal deflection current, where Ly is the inductance of the deflection coil and Tr is the time width of the horizontal retrace period.

Next, when the changeover switch 10 is switched to the a side, a pulse generated in the tertiary winding 9 and having approximately the same waveform as the above-mentioned negative side pulse and a low voltage is horizontally deflected via the S-shaped correction condenser 5. It is applied to the other end of the coil 4.

Therefore, if the amplitude of this low voltage pulse is Vc'p, then the horizontal deflection coil 4 has the following equation: Vcp-Vc'p = Vc''p(
7') This is approximately the same as if the primary side pulse with the amplitude was applied.

Therefore, as can be seen from the above equation, the changeover switch 10
When is on the a side, the amplitude of the horizontal deflection current ■y is higher than when on the b side
becomes smaller, and therefore the horizontal width of the screen decreases.

At that time, in order to reduce the horizontal width, that is, the amplitude IY of the deflection current by about 10%, the primary side pulse Vcp is
It is sufficient to reduce the secondary side pulse Vc' by that amount.
According to the inventor of the present invention, the number of turns of the tertiary winding 9 required to set p to Vc'p = 0 and I Vcp is approximately 10 turns for a 14-inch television receiver. Compared to the width adjustment coil shown in Figure 2, its inductance is extremely small, so it hardly affects the deflection current waveform.Figure 4 shows the horizontal frequency switching type horizontal deflection circuit explained at the beginning. This figure shows a preferred embodiment when implemented in a television receiver, and parts corresponding to those in FIG. 3 are given the same figure numbers.

In the circuit shown in FIG. 4, an auxiliary capacitor 11 for three-character correction is connected between the other fixed terminal of the changeover switch 10 and the ground point.

Further, an intermediate tap B is provided on the primary winding 7 of the flyback transformer, and this tap is connected to a switch 12 which is linked to the changeover switch 10 (both of which are linked to a horizontal frequency changeover switch such as a horizontal oscillation circuit). The one with lower horizontal frequency is connected to terminals a and a', and the one with higher horizontal frequency is connected to terminals b'
, respectively) are connected to one of the fixed terminals b'.

The other fixed terminal a' of this changeover switch 12 is connected to one end A on the low potential side of the negative side winding 7, and a diode is connected between the movable terminal C' and the DC power supply (+Vcc). 13 are connected.

Further, a capacitor 14 is connected between the intermediate tap B and the power supply (+Vcc).

Here, the reason why the diode 13 and the capacitor 14 are provided to boost up the power supply voltage and apply it to the horizontal output transistor 1 when the switch 12 is switched to the b side is because the switches 10 and 12 are aa' In order to increase the amount of adjustment of the horizontal width (in the direction of decreasing the width) when switching to the side, the number of turns of the tertiary winding 9 must be increased, but if this is done, the flyback transformer 6 is difficult to design due to the relationship between distributed capacitance and leakage inductance, and also has the disadvantage that it becomes large.

Therefore, by setting the power supply voltage (+VCC) relatively small, it is possible to obtain a deflection current of a predetermined amplitude in the case of the aa' side without increasing the number of turns of the tertiary winding 9. In the case of the bb' side, the power supply voltage is substantially increased so that the deflection current can be greatly changed.

That is, when the switch 12 is switched to the b' side,
When +Vcc is applied to the intermediate tap B of the primary winding 7, and the horizontal output transistor is activated thereby, a voltage at the A end of the primary winding 7 is generated with an amplitude proportional to the turns ratio between AC and AB. The pulse voltage shown in Figure 5 is generated, and the capacitor 14 is charged with this pulse voltage, so the A terminal ends up with +
A DC voltage of +Vc'c higher than Vcc will appear, and since this +Vc'c is applied to the horizontal output transistor 1 via the AC terminal of the winding 4, the amplitude of the deflection current at this time is The voltage increases by the amount that +Vcc rises to +Vc'c, and therefore the horizontal width of the screen increases.

Moreover, the auxiliary capacitor 11 is connected and separated by the changeover switch 10.
This is to ensure that this correction operation is not impaired even if the horizontal frequency changes, since this composes a weak series resonant circuit with the horizontal deflection coil 4 to correct the waveform of the horizontal deflection current.

In the embodiment shown in FIG. 4, the operating voltage of the horizontal deflection circuit changes by switching the changeover switch 12, so
The amplitude Vcp of the flyback pulse that appears at the C end of the plane also changes, and therefore the picture tube anode voltage and screen voltage also change slightly, and the direction of the change is in a direction that prevents the horizontal width from changing due to changes in the deflection current. Yes, but
Since the degree of change in the horizontal width due to the former is smaller than that due to the latter, the horizontal width can be controlled by changing the power supply voltage.

Also, if such a horizontal deflection circuit is used in a zoom TV to increase the horizontal width, the increased horizontal width will reduce the average beam current of the picture tube, thus reducing the average screen width. Although the brightness will decrease, the increase in the anode voltage and screen voltage of the picture tube will work to increase the average brightness of the screen, thus compensating for the brightness change due to horizontal width switching. This is convenient because it allows you to

As described above, in the horizontal deflection circuit of the present invention, the flyback transformer is provided with a tertiary winding for horizontal width adjustment, and the low voltage pulse taken out from the tertiary winding is transferred to the primary of the flyback pulse through a changeover switch. Since the voltage is applied to the other end of the horizontal deflection coil whose one end is connected to the winding, there is no need for multiple power supplies with different voltages.
Moreover, the horizontal width can be adjusted and changed efficiently without waveform distortion of the deflection current, and since no external parts are required other than the changeover switch, it can be realized at low cost. It is suitable for horizontal deflection circuits with horizontal width adjustment for ordinary television receivers, horizontal frequency switching type receivers, and horizontal deflection circuits for zoom televisions.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams showing conventional horizontal deflection circuits, Figure 3 is a circuit diagram showing the horizontal deflection circuit of the present invention, and Figure 4 is a circuit diagram of the present invention implemented in a frequency-switchable horizontal deflection circuit. FIG. 5 is a circuit diagram illustrating an embodiment in which the circuit shown in FIG. 3 is operated. 1: Horizontal output transistor, 4: Horizontal deflection coil, 6:
Flyback transformer, 9: Tertiary winding, 10: Selector switch.

Claims (1)

[Scope of utility model registration request] A flyback transformer whose primary winding is connected to the horizontal output transistor and one end of the horizontal deflection coil is provided with a tertiary winding for horizontal width adjustment, and a low-voltage flyback pulse taken out from the tertiary winding is switched using a switch. A horizontal deflection circuit characterized in that the voltage is applied to the other end side of the horizontal deflection coil through the switch, and the deflection amplitude is adjusted by switching the changeover switch.