JPS6114226Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a circuit for extracting low DC voltage and horizontal pulses using a flyback transformer provided in a horizontal output circuit in a television receiver. In a typical television receiver, in addition to the high voltage supplied to the picture tube anode, a flyback transformer provided in the horizontal output circuit obtains a low voltage for the DC operating power supply for the circuit inside the receiver and a horizontal pulse for blanking operation. That's what I do. FIG. 1 shows a conventional horizontal output circuit configured in this manner, in which 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a damper diode, 4 is a resonant capacitor, 5 is a horizontal deflection coil,
6 is an S-shaped correction capacitor, 7 is a dropper resistor,
8 is the primary winding of the flyback transformer 9 , 10 is 2 for voltage for taking out the picture tube anode voltage.
The next winding, 11, is a low voltage tertiary winding for extracting DC low voltage and horizontal pulses; this tertiary winding 1
The intermediate tap b of 1 is grounded, and a positive horizontal pulse for blanking pulses and keying pulses of the keyed AGC circuit is taken out from its high potential side terminal a, and the low potential side terminal c of the tertiary winding 11 is taken out. A diode 12 and a capacitor 13 rectify and smooth the horizontal pulse of negative polarity that appears in the horizontal pulse, so that a low DC voltage (4, for example, 18 V) of positive polarity is extracted. At this time, the reason why the negative polarity pulse is rectified to obtain the positive polarity DC voltage is that this reduces the ripple in the horizontal period compared to the case where the positive polarity pulse is rectified.
This is based on the fact that the horizontal scanning period Ts is sufficiently longer than the retrace period Tr. FIG. 2 shows a horizontal pulse appearing at the high potential side terminal a of the circuit of FIG. 1, but the problem with this pulse is that ringing A occurs during the scanning period Ts. This ringing is caused by the leakage inductance and distributed capacitance between the secondary winding 10 and the primary winding 8 in order to stabilize the high voltage pulse appearing in the secondary winding 10 and increase its generation efficiency. Flyback transformer 9 performs harmonic tuning determined by
This occurs as a result of harmonic components appearing in the tertiary winding 11 when the Therefore, 3
When rectifying and smoothing a horizontal pulse of opposite polarity to that shown in Fig. 2 appearing at the low potential side terminal c of the next winding 11 (this pulse also naturally causes ringing similar to that shown in Fig. 2), the ripple caused by this ringing is will remain in the DC voltage. Also, considering the pulse itself in Figure 2, the part of this pulse that can be used as a blanking pulse is the positive polarity part above the reference level shown by the thin line, so the blanking period is longer than the original retrace period Tr. It will be slightly shorter. Furthermore, in the case of FIG. 1, since pulses of opposite polarity must be taken out from terminals a and c, the windings between a and b and between b and c must be independent, and therefore 3 The number of turns of the secondary winding 11 becomes considerably large, which hinders the reduction in size and weight of the flyback transformer. However, the present invention eliminates these drawbacks and will be described in detail below. FIG. 3 shows an embodiment of the horizontal output circuit of the present invention. Parts corresponding to those in FIG. A rectifier diode 12 is connected between the high potential side terminal a' of the tertiary winding 11 and the ground point in the direction shown in the figure, and a smoothing capacitor is connected between the low potential side terminal c' of this tertiary winding 11 and the ground point. 13 is connected so that a positive DC low voltage is taken out from the ground point between this capacitor and the low potential side terminal, and a positive horizontal pulse is taken out from the intermediate tap b' of the tertiary winding 11. This is the point I made. That is, as can be seen from FIG. 2, the high potential side terminal of the tertiary winding 11 in FIG.
Since a' has a lower potential than the low potential side terminal c' during the scanning period Ts, the diode 12 is turned on and current flows in the loop shown, and this current charges the capacitor 13. A DC voltage of the illustrated polarity is generated between both ends of 13. On the other hand, since the diode 12 is off during the retrace period Tr, a positive pulse is generated at the high potential side terminal a'. Therefore, the voltage waveform appearing at the terminal a' becomes as shown in FIG. It should be noted here that in the voltage waveform in Figure 2, the AC and DC reference levels are both at the positions indicated by the broken lines in the figure, whereas in the voltage waveform in Figure 5, the AC reference level is This is the position of the broken line, and the DC reference level is the position of the solid line (thin line).
This is due to the AC pulse generated in the tertiary winding 11 and the DC voltage Eo generated at its low potential terminal c'.
This is because they are superimposed. Furthermore, ringing does not occur in the voltage waveform of FIG. 5, but this is due to the following operation. That is, FIGS. 6a and 6b are simplified diagrams for explaining the ringing suppression operation, where 14 represents the source of the ringing voltage A appearing in the tertiary winding 11, and 12 and 13 represent the diodes shown in FIG. 3, respectively. and a capacitor, and 15 is the tertiary winding 1
DC voltage taken out from low potential side terminal c′ of 1
It represents the load resistance of Eo. Now, when the upper side of the ringing source 14 is negative (lower than Eo) (Fig. 6a), the diode 12 is turned on and the negative peak of the ringing waveform A is clamped to the potential Eo. rectified. At this time, a positive voltage (if higher than Eo) is generated below the ringing source 14, but this is absorbed by charging the capacitor 13 in the direction shown. In the next half cycle of the ringing waveform A, when the upper side of the ringing source 14 becomes positive and the lower side becomes negative (FIG. 6b), the diode 1
2 is not conductive, and the charge stored in the capacitor 13 is discharged through the resistor 15. At this time, since the time constant of this discharge loop is sufficiently long compared to the horizontal period, there is no risk that the DC voltage Eo appearing on the capacitor 13 itself will be discharged. By repeating such an operation once or twice, ringing can be completely suppressed. This is because ringing becomes a normal AC power supply, and if it is suppressed at some point, it will not continue to occur until the next generation operation. As described above, the voltage waveform shown in FIG. 5 appears at the high potential side terminal a' of the tertiary winding 11, which means the following. That is, first of all, since the ringing occurring in the tertiary winding 11 is suppressed, the DC voltage Eo obtained from the low potential side terminal c' does not include ripples due to ringing and is stable. Secondly, in the voltage waveform shown in Figure 5, the DC reference level is lower than the AC reference level, so when this pulse is used as a blanking pulse, the blanking pulse is lower than when the one in Figure 2 is used. As the width of the period becomes wider, reliable blanking operation can be expected. The same thing can be said about the case where a pulse having a smaller peak value than the one in FIG. 5 is obtained from the intermediate tap b of the tertiary winding 11 and used as a blanking pulse as in the embodiment shown in FIG. You can also say Furthermore, in the embodiment shown in FIG. 3, the number of turns between b' and c' = a, the number of turns between b, and the number of turns between a' and c' = b, compared to the conventional example shown in FIG. , c, the number of turns of the tertiary winding 11 as a whole can be reduced. This also applies to the case where it is necessary to extract a horizontal pulse with a larger peak value than the pulse for extracting a DC low voltage (Fig. 5), as in the embodiment shown in Fig. 4. In that case, b'', Number of turns between c″ = b, number of turns between c, a″,
The number of turns between a and b should be the number of turns between a and b. As described above, according to the present invention, the DC low voltage used as the operating power source of each circuit in the television receiver and the blanking Horizontal pulses used for pulses, etc., with a sufficiently wide blanking period and without ringing can be extracted efficiently and stably from the flyback transformer, and are suitable for implementation in the horizontal output circuit of television receivers. It is.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional horizontal output circuit, FIG. 2 is a waveform diagram of horizontal pulses extracted therefrom, FIGS. 3 and 4 are circuit diagrams showing different embodiments of the horizontal output circuit of the present invention, FIG. 5 is a waveform diagram of horizontal pulses extracted from them, and FIGS. 6a and 6b are equivalent circuit diagrams for explaining the ringing suppression operation. 2... Horizontal output transistor, 9 ... Flyback transformer, 11... Tertiary winding, 12... Rectifier diode, 13... Smoothing capacitor.

Claims (1)

[Scope of utility model registration request] A low voltage tertiary winding having an intermediate tap is provided in the flyback transformer connected to the horizontal output transistor, and the grounding point is connected to the anode between the high potential side terminal of the tertiary winding or the intermediate tap and the grounding point. A rectifying diode is connected so that the voltage is on the side, a smoothing capacitor is connected between the low potential side terminal of the tertiary winding and the above grounding point, and a smoothing capacitor is connected between the connection point of the capacitor and the low potential side terminal. The obtained positive polarity DC low voltage is supplied to a load having impedance, and a positive horizontal pulse is supplied from the high potential side terminal of the tertiary winding and the terminal on the intermediate tap side to which the diode is not connected. 1. A horizontal output circuit for a television receiver, characterized in that the .