JPS5840690Y2 - horizontal deflection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horizontal deflection circuit for a television receiver, and more particularly to a horizontal centering circuit included in this circuit.

Conventional horizontal centering circuits usually consist of a variable resistor that adjusts the centering current flowing through the horizontal deflection coil, and a changeover switch that switches the direction of the centering current, but centering can be easily performed without providing this changeover switch. There is a device that allows you to make adjustments.

FIG. 1 shows an example of this horizontal centering circuit, and 1 is the output stage of a commonly known horizontal deflection circuit.

The horizontal output stage 1 has a horizontal output transistor Q1, and an input terminal 2 connected to its base is supplied with a drive signal S1 based on a switching signal (pulse signal) synchronized with the horizontal period obtained by a horizontal oscillator. This drive signal S1 controls on/off of the transistor Q1.

As shown in the figure, a series circuit consisting of a damper diode 3, a resonance capacitor 4, a horizontal deflection coil 5, and a three-figure correction capacitor 6 is connected between the collector and emitter of the transistor Q1 to form a horizontal output stage 1. Ru.

In addition, the operating voltage V ((() from the terminal 7 to the horizontal output voltage 8
is supplied to the collector of the transistor Q1 via the primary coil 8a.

Therefore, by turning on and off the transistor Q1, a sawtooth horizontal deflection current □ as shown in FIG. A sinusoidal voltage Va (hereinafter this voltage will be referred to as an inter-terminal voltage) is generated.

A horizontal centering circuit 20 is connected between the connection midpoint 11 of the series circuit consisting of the horizontal deflection coil 5 and the capacitor 6 and the power supply terminal 7.

The horizontal centering circuit 20 is connected to the connection midpoint 11 as shown.
a horizontal centering coil 11 having one end connected to
A, and a centering current control section 12 interposed between the other end and the power supply terminal 7.

The control unit 12 includes a pair of diodes D1. D2, and these are connected so that they have opposite polarities, and the electrodes on the centering coil 11A side are commonly connected to this coil 11, and the other electrode on the power terminal 7 side is a variable impedance The element is connected to the power supply terminal 7 via a variable resistor 13 in this example.

Centering adjustment of such horizontal centering circuit 20 will be described below.

First, in the variable resistor 13, the resistance value R on the diode D1 side and the resistance value R2 on the diode D2 side are equal (R.

R2) Consider the state.

In this case, the diodes D□ and D2 are conductive when they are in a voltage relationship such that the voltages applied across them are in the forward direction with respect to the respective diodes DI and D2.

On the other hand, the power supply voltage ■. 0 (for example, 130 V) and the voltage Va between the terminals of the three-character correction capacitor 6 have the relationship shown in FIG. A forward voltage is applied across only the diode D1, and the diode D1 becomes conductive.

As a result, a current IDI flows through the centering coil 11A to the diode D1 in the direction shown by the arrow a (Fig. 2C).
flows.

However, at the point when the current ID begins to flow (when the diode D1 becomes conductive), the centering coil 11A is placed in the current path.
, the time t1' is delayed from the time t1, and similarly, the time when the diode D□ becomes non-conductive (off) shifts from t2 to t2'.

On the other hand, during the period T2 (times t2 to ta), contrary to the above, the inter-terminal voltage Va becomes lower than the power supply voltage Vcc, and only the diode D2 becomes conductive.

Therefore, a current ID2 (FIG. 2D) flows in the direction indicated by the arrow through the diode D2 between time points t2' and t3'.

Note that the current ID2 in this case is approximately equal to the current iD1 when the diode D1 is turned on.

Here, since the centering current ■ flowing through the centering coil 11A is I''IDI ID2, the period T
1. Centering current in Figure 2 E through T 2■
flows.

However, since the current values of the currents IDI and ID2 are both equal, the average value of the currents is zero, and a direct current equal to the difference between the currents IDI and 102 does not flow through the horizontal deflection coil 5. Therefore,
The position of the raster is immovable.

Therefore, even if the raster position is shifted from the center of the screen to the right side, the raster exists at that position.

In such a case, the raster position can be moved to the left by adjusting the variable resistor 13 so that the resistance value becomes R1<R2 and directing the centering current flowing through the horizontal deflection coil 5 downward. can.

Next, I will explain it. R1<R2, for example, R1 is zero and R
When the variable resistor 13 is adjusted so that 2 takes the maximum value,
The conduction periods of the diodes D1 and D2 are respectively controlled for reasons to be described later. For example, the conduction periods of the diodes D1 and D2 in the above-mentioned operation description are respectively controlled by W1.D2. If W2 is W2, then Wl and W2 in the previous explanation, but if the resistance value R1 is smaller than R2 as in this example, the conduction period W1 of the diode D1 is longer than W2 <(Wl>W2) Become,
The current IDI, 102 changes as IDI>ID2.

Therefore, in this example, the current IDI shown in FIG. 3B and C,
ID2 is each diode D1. It will flow through D2,
As a result, the centering current (2) becomes as shown in the third diagram, and its average value does not become zero, and a downward centering current flows through the horizontal deflection coil 5, allowing the raster position to be moved to the left.

Note that the peak-to-peak value of the centering current (2) is approximately the same as the centering current (2) in FIG. 2E because its maximum value is suppressed by the presence of the centering coil IIA.

By the way, the conduction period W1. of the diodes D□, D2. W2
Although it has been stated that the resistance values R1 and R2 are controlled, the similarities thereof will be explained next.

Now, as the resistance value R is made smaller, the current IDI passing through the diode D1 becomes easier to flow, so in this case, the impedance of the centering coil 11A is more dominant than the resistance value R1, and the voltage due to the resistance value R is descent and
Ignoring the forward voltage drop of the diode D1, the voltage e applied across the centering circuit 20 is as follows.

However, L is the inductance of the centering coil 11A.

Here, during the period T1 shown in FIG. 3, since a positive voltage is applied to the centering coil IIA, the L-di
/dt>O, and the current 101 continues to increase, but at time t2 after the period T1, the current IDI becomes L-di/dt-0, so the current IDI takes the maximum value.

However, after time t2, since L-di/dt<0, the current 101 begins to decrease.

Therefore, the current ID1 can flow even if the voltage e applied to the centering circuit 20 becomes negative (period T2).
The current waveform will be as shown in Figure B.

In other words, it is considered that a part of the energy stored in the 5-character correction capacitor 6 is exchanged between this capacitor 6 and the horizontal centering coil IIA, and therefore the L-di/ When dt>0, energy is being transferred from the capacitor 6 to the centering coil 11A, and when I, -di/dt<O, the energy transferred to the centering coil 11A is returning to the capacitor 6.

Therefore, considering the case where the resistance value R□ is increased, L-d
During the period when i/dt>O, the energy that should be transferred from the capacitor 6 to the centering coil 11A is consumed by the resistor 13a, and during the period when 1-di/dt<O, the energy transferred to the centering coil IIA is consumed again. The energy is consumed due to the presence of the resistor 13a, and if the resistance value R□ is increased, the attenuation of the energy exchanged between the capacitor 6 and the coil IIA becomes faster, and the energy is dissipated by the diode D0.
Regarding this, the non-conducting state occurs more quickly than when the resistance value R1 is small.

At the same time, the maximum value of the current iD1 is also limited by the resistor 13a.

Therefore, if the variable resistor 13 is adjusted so that R1<R2 as in the above example, the conduction time W1 of the diode D1
becomes longer than that of diode D2, W2, and iD
The relationship □>iD2 is established, and the current waveforms shown in FIG. 3B-D are obtained, thus the raster moves to the left.

In this case, the variable resistor 13
By adjusting , you can position the raster in the center of the screen.

When the variable resistor 13 is adjusted so that R1>R2, the operation is completely opposite to that described above, the raster moves to the right, and the current waveforms at each part at that time are as shown in Figure 4 B-D. become.

By the way, in order to obtain a stable medium-high voltage from the secondary side of a flyback transformer, that is, with good regulation, the inductance of the primary coil of this transformer has recently been increased. If it is increased, for example, when the high-voltage load current fluctuates greatly, the amplitude of the collector output (voltage or current) of transistor Q1 may change in response to this load fluctuation.

The change in amplitude appears as a fluctuation in the terminal voltage of the capacitor 6, that is, a ripple voltage is generated.Therefore, a ripple current corresponding to the ripple voltage flows through the centering circuit 21, which may impair the stability of the screen.

The present invention takes these points into consideration and aims to stabilize the screen with an extremely simple configuration.

That is, in the present invention, as shown in FIG.
Horizontal centering coil 11A between and connection midpoint 11
A parallel circuit 11 consisting of a capacitor 11B and a centering coil IIA is provided, and the centering coil IIA is selected to have an inductance value sufficient to suppress the above-mentioned notch plumic current, thereby preventing ripple current from flowing into the centering circuit 20.

The inductance value when not considering screen shaking due to ripple current varies depending on the model, but is 1.5 to 2.
It is about mH.

On the other hand, in order to eliminate the adverse effects of ripple current, it is desirable to select a value that is at least 10 times the conventional value.

Of course, this value varies depending on the degree of load fluctuation, and in this example, it is selected to be about 15 to 49 mH.

If the inductance value is selected to be sufficiently large in this way, the direct current of the centering current (■) will be insufficient and the amount of movement of the raster will be reduced. Capacitors 11B are connected in parallel and the current flowing through them compensates for the lack of direct current.

Since a horizontally periodic sawtooth wave current as shown in FIG. 2A flows through the capacitor 11B, a normal centering current I and a composite current of this sawtooth wave current flow through the centering circuit 20 to compensate for the shortfall in the DC current. compensation will be made.

This sawtooth wave current is also superimposed with the ripple component due to the load fluctuation described above, but since this ripple component is an alternating current component, it does not affect the centering adjustment.

Incidentally, since the capacitor 11B also acts as a capacitor for the 5-character correction, the 3-character correction amount of the horizontal deflection current IH flowing through the deflection coil 5 is determined by the combined capacitance of the capacitors 6 and 11B.

Therefore, the capacitance of capacitor IIB should be determined by the setting of the raster movement amount on the screen and the above-mentioned 3-character correction amount, and this example uses a capacitance that does not affect the 3-character correction and allows sufficient centering adjustment. In this case, the capacitance of capacitor 6 was selected to be as luxurious as possible.

As mentioned above, it was confirmed that when inductance and capacitance were selected, the screen did not shake due to ripple current, and sufficient centering adjustment could be made without affecting the 3-character correction.

As explained above, according to the configuration of the present invention, it is possible to reliably prevent screen shaking that occurs due to load fluctuations without affecting three-character correction, and to ensure screen stability.

Note that in the above-described embodiments, other impedance elements such as coils can be used in place of the variable resistor 13.

A flyback transformer may be connected in place of the horizontal output transformer 8.

[Brief Description of the Drawings] Figure 1 is a connection diagram showing an example of a horizontal deflection circuit, Figures 2 to 4 are waveform diagrams for explaining the operation, and Figure 5 is an example of a horizontal deflection circuit according to the present invention. FIG. 1 is a horizontal deflection output stage, Q□ is an output transistor, 5 is a horizontal deflection coil, 6 is a capacitor for figure 5 correction, 8 is a horizontal output cadence, 20 is a horizontal centering circuit, 11A is a horizontal centering coil, 12 is a center non-gum current control 13 is a variable impedance element, and 11B is a capacitor.

Claims (1)

[Scope of utility model registration request] In a horizontal deflection circuit in which a horizontal output transistor is connected in series to the primary coil of a horizontal output quadrance, and a series circuit of a horizontal deflection coil and a capacitor for figure 3 correction is connected between the collector emitter of this horizontal output transistor, Connect one end of a parallel circuit of a horizontal centering coil and a capacitor to the connection midpoint of the circuit, and connect the other end of the parallel circuit to the common connection point of one of a pair of diodes connected with opposite polarities. A variable impedance element for adjusting the centering current is connected between the other ends of the pair of diodes, and its sliding terminal is connected to the DC power terminal of the second coil to form a horizontal centering circuit. The coil is 2 of the above horizontal output cadence.
A horizontal deflection circuit provided on the next side is selected to have a value sufficient to suppress the current based on the ripple voltage generated at the connection midpoint due to load fluctuations.