JPS6024626B2 - television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television receiver that performs operation switching according to television signals having different horizontal deflection frequencies.

In general, the horizontal deflection frequency of television signals differs depending on the broadcasting system of each country. For example, in France, UHF is 1562 Hz (625 horizontal scanning lines), and VHF
In this case, the frequency is 2047 Hz (819 Hz).

Therefore, in order to be able to receive television signals with different horizontal deflection frequencies on a television receiver with a single horizontal deflection circuit, the magnitude of the horizontal deflection current must be constant even when the deflection frequency is switched. It is necessary that the magnitudes of the high voltage and low voltage DC voltages that are kept substantially constant and supplied to various parts within the television receiver do not change significantly. However, the present invention provides a novel horizontal zero deflection frequency switching type television receiver that eliminates the conventional drawbacks by considering the above points from various viewpoints.

An embodiment of the television receiver of the present invention shown in FIG. 1 will be described below.

1 is a pair of power supply input terminals connected to a 110V or 220V AC power source; 2 is a rectifying and smoothing circuit consisting of diodes 3, 4 and capacitors 5, 6; Operates as a half-wave rectifier circuit at 220V input), and operates as a half-wave rectifier circuit at contact L side (at 110V input).
It is horizontally configured to operate as a voltage doubler rectifier circuit.

Reference numeral 8 denotes a control transistor 9 connected in series to the output terminal of the rectifying and smoothing circuit 2, a variable resistor 10 for output voltage division connected to the emitter of the transistor, and a voltage obtained at the movable element of the variable resistor as a reference voltage. This is a continuous control type constant voltage circuit consisting of an error detection circuit 11 that compares and amplifies the voltage.

Reference numeral 12 denotes a horizontal oscillation circuit equipped with a horizontal AFC function to which a horizontal synchronizing pulse 13 separated from the television input signal is applied, and this circuit is an IJ near ICLA-
It consists of 1 spot 4, and the number surrounded by 0 marks represents the pin number.

This IC is designed to be able to vary the oscillation frequency by changing the magnitude of the DC voltage applied to pin ■, but in this case, the duty cycle of the oscillation output pulse is kept constant (50%). being considered. That is, the resistors 14, 14', the changeover switch 15, and the variable resistor 16 connected between the pin (2) and the output terminal of the constant voltage circuit 8 are the circuit connections for switching the oscillation frequency.
Note that the diode 17 connected to the connection point between the pin ■ and the resistor 14 is for obtaining the operating power supply voltage of 11 V for the IC, and the circuit consisting of the resistor 18 and capacitors 9 and 20 connected to the pin ■ is a horizontal AFC. This is for integrating and supplying a flyback pulse fed back from a flyback transformer, which will be described later, for operation. Reference numeral 21 denotes a horizontal drive circuit consisting of a transistor 22 which receives the oscillation output pulse of the horizontal oscillation circuit 12 and a coupling transformer 23 connected to its collector, and the secondary side output of the coupling transformer connects resistors 24 and 25, respectively. The configuration is such that the signal is supplied to the DC-DC converter circuit 26 and the horizontal output circuit 27 via the DC-DC converter circuit 26 and the horizontal output circuit 27.

The converter circuit 26 includes a switching transistor 28 whose base input is the output of the horizontal drive circuit 21.
The converter transformer 29 is inserted between the collector of this transistor and the output end of the constant voltage circuit 8, and this circuit connects the secondary windings -, n3, and n4 of the converter transformer to the primary It is a great advantage to have the same polarity as the side winding n, and to connect a capacitor 30 in parallel with the primary winding, which is sufficiently larger than the distributed capacitance of this winding, to achieve resonant same polarity operation. Features.

That is, Fig. 2 shows the operating waveforms of each part of the converter circuit 26. Fig. 2 shows the base voltage of the switching transistor 28, Fig. 2 shows its base current, Fig. 2 shows its collector voltage, and Fig. 2 shows the base voltage of the switching transistor 28. The collector current is represented by the voltage Vo across the secondary winding.
It represents the FF period and the resonance period. As can be understood from the figure, the period t4 from the end of the resonance period rule 3 to the beginning of the ON period is the base of the switching transistor 28.
Since conduction occurs between the collectors and a so-called damper operation is performed, even if the oscillation frequency of the horizontal oscillation circuit 12 is switched, t3<
If the resonant frequency of the converter circuit 26 is selected to satisfy t2, the output voltage V. The positive peak value Vp is determined by Vp=Vcc/N, where N is the winding ratio between the primary and secondary, and is stabilized. The resonance frequency may be selected slightly higher than the higher oscillation frequency since the 50% duty cycle of the output pulse of the horizontal oscillation circuit 12 does not change due to switching of the oscillation frequency.

At this time, it goes without saying that it is necessary to take into consideration that the OFF period shown in FIG. 2 is slightly shorter than the ON period t due to the accumulation period of the base current of the transistor 28. Each winding on the secondary side of the converter transformer 29, ratio,
Rectifying and smoothing circuit 31 with a large discharge time constant connected to n4
, 32, 33 respectively take out DC voltages of 153V, 18V, and 6.3V, and the winding n2
A 110V DC current is taken out from the middle tap of
This 18V is supplied as an operating power supply to each circuit of the television receiver, 6.3V is supplied as a heater power supply for image reception, and 110V and 153V are supplied as an operating power supply to a horizontal output circuit 27, which will be described later. .

In particular, the 220V constant voltage output of the constant voltage circuit 8 is directly used as the operating power supply for the video output circuit and the audio output circuit, and the 110V is supplied to the vertical deflection circuit as the operating power supply. There is. The horizontal output circuit 27 includes a damper diode 35, a resonant capacitor 36, and a horizontal deflection coil 3 at the collector of a horizontal output transistor 34 that is switched by the output of the horizontal drive circuit 21.
There is no difference from the conventional circuit in that 7 is connected, but
A second changeover switch 39 that operates in conjunction with the first changeover switch 15 is connected to the other end of the primary winding na of the flyback transformer 38, one end of which is connected to the collector of the transistor 34, and one of its contacts b. A 153V DC voltage obtained from the secondary winding n2 of the converter transformer 29 is connected to the converter transformer 29, and a 110V DC voltage obtained from the intermediate tap of the above wires is connected to the other contact a, and the horizontal deflection coil One of the S-shaped correction capacitors 40, 40' connected in series with 37, 40' is separated by a third switch 41 that moves to the first and second cut-off switches 15, 39. It is characterized by

The reason why the DC operating voltage supplied to the horizontal output transistor 34 via the primary winding na of the flyback transformer 38 is switched according to the horizontal deflection frequency is that the operating voltage is set to V and the horizontal deflection current is scanned. If the period is ts and the amplitude of the horizontal deflection current is im, then V=L・
Since there is a relationship between im/ts, it is necessary to change the magnitude of the operating voltage V in order to keep the magnitude of the deflection current im constant even if the horizontal deflection frequency changes and the magnitude of the scanning period ts changes. Also, the reason why the capacitor 40' is adjusted according to the horizontal deflection frequency is that the S-shaped correction capacitor composes a weak series resonant circuit with the horizontal deflection coil to correct the waveform of the horizontal deflection current. This is to ensure that even if the frequency changes, this waveform correction effect will not be impaired and the amplitude of the horizontal deflection current will not change. Furthermore, the horizontal output circuit 27
The parallel resonance frequency determined by the inductance of the horizontal deflection coil 37 and the flyback transformer 38, and the distributed capacitance of the resonant capacitor 36 and the transformer 38 is set to be approximately constant (10 mountain seconds) regardless of the switching of the horizontal deflection frequency. It is characterized by what it did.

The reason for this is that the high voltage winding nb of the flyback transformer 38,
In order to stabilize the output voltage taken out from the NC, so-called high-frequency tuning of the flyback pulse is performed for both of the above-mentioned two horizontal deflection frequencies. As is well known, in both cases, the distributed capacitance of the resonant capacitor 36 and flyback transformer 38 is adjusted at the deflection frequency so that the ratio Z=tf/tc between the horizontal repetition period tc and the retrace period tf does not change. However, it is impossible to switch this distributed capacitance based on the circuit, and the withstand voltage of the changeover switch used for it is also a problem, so it is not possible to perform harmonic tuning in both of the above cases. This is because it is practically impossible, and in that case, the practical benefit of switching the retrace period tf of the horizontal deflection circumferential current according to the deflection frequency will be reduced. In addition, the retrace period on the television signal side is 12 seconds in the case of VHF in the French system mentioned above, and in the case of UH
In the case of F, it is 9.5 seconds, so if the retrace period tf of the horizontal deflection coil is fixed at 10 r seconds, the raster scanning period will be different from the video signal scanning period, and the size of the image on the cathode ray tube will change. However, this degree of difference is not a problem in practical terms. A double voltage rectifier circuit 42, a linking suppression circuit 43, and a voltage dividing resistor 44 are connected to one winding nb on the secondary side of the flyback transformer 38, and the anode voltage and focus voltage of the picture tube are extracted from the other. winding nc
A rectifying and smoothing circuit 45 of a diode and a capacitor is connected to the circuit so that the screen grid voltage of the picture tube is taken out, and the flyback pulse taken out from the center tap of the winding nc is connected to the above-mentioned integrating circuit. The signal is supplied to the horizontal oscillation circuit 12 through the horizontal oscillation circuit 12.

In the case of the above-mentioned French method, switching the first, second, and third changeover switches 15, 39, and 41 to the contact a side corresponds to UHF (fH = 1562 pitch ratio), and the case where the contact b
The case of switching to the side corresponds to VHF (fH = 2047 county town z), but now, as V,: 110V, the DC operating voltage V (=V, or V2) and the primary side flyback pulse in each case are The positive peak value Vp is calculated using the previous formula V=L・i/ts (where L and im are constant) and the high pressure relational formula Vp=
If you calculate it using V Note Chapter 221, it will look like the table below.

According to this table, the change in Vp due to switching of the deflection frequency fH is less than 1%, and therefore the change in the output voltage on the secondary side is also considered to be about this amount. The difference in degree does not impede the deflection operation. As detailed above, the television receiver of the present invention does not require switching the tap of the flyback transformer in order to boost up the operating voltage to the horizontal output circuit.
When high frequency tuning is performed for one deflection frequency without changing the inductance or distributed capacitance, the deviation from the other deflection frequency becomes smaller.

By switching the '21 S-correction capacitor, the S-correction operation is not compromised for each deflection frequency and the amplitude of the horizontal deflection current remains exactly constant.

Since the low voltage required in the {31 receiver is obtained from the DC-DC converter circuit, there is no need to switch the low voltage winding as in the case of extracting it from the flyback transformer, and the flyback transformer becomes smaller. '4) Since the converter transformer is of the intermittent operation type, the transformer can be made smaller compared to the method of extracting the low voltage from the power transformer.

'5} Since the converter circuit operates in a resonant type with the same polarity, its DC output voltage is approximately determined only by the turns ratio between the primary and secondary, so it is extremely stable and requires control for stabilization. The circuit configuration is simple without requiring a loop or the like, and is almost unaffected by switching the deflection frequency.

■ Since the connection of the rectifier circuit can be switched for different commercial power supply voltages, a power transformer is not required, contributing to the size and weight of the receiver.

It has many advantages such as, and is of great industrial value when used in horizontal deflection frequency switching type television receivers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing the main structure of an embodiment of the television receiver of the present invention, and FIG. 2 is an operational waveform diagram of the external portion thereof. 2: Rectifier smoothing circuit, 8: Constant voltage control circuit, 12: Horizontal oscillation circuit, 21.: Horizontal drive circuit, 26: DC-DC
Converter circuit, 27: Horizontal output circuit. Figure 2 of the ship

Claims (1)

[Claims] 1. A television receiver in which the number of scanning lines is switched according to television signals having different horizontal deflection frequencies,
a horizontal deflection circuit which receives as input the output of a horizontal oscillation circuit whose oscillation frequency can be switched; and a DC deflection circuit which receives as input the constant voltage rectified output of a commercial AC power supply and is driven by switching in synchronization with the output of the oscillation circuit. A television receiver comprising a DC converter circuit and a circuit connection for switching different output voltages of the circuit and supplying the same to the horizontal deflection circuit. 2. The converter circuit performs a same polarity operation in which the waveform on the secondary side due to switching has the same polarity as the waveform on the primary side,
The television receiver according to claim 1, wherein the television receiver performs resonance operation during a switching off period. 3. In the converter circuit, the collector-emitter of a switching transistor to which the output of the oscillation circuit is applied to the base is connected in series with the primary winding of the converter transformer with respect to the constant voltage rectified output; 3. The television receiver according to claim 2, wherein a resonance capacitor is connected in parallel and the output voltage is obtained from the secondary winding of the transformer. 4 The converter transformer is 2
4. The television receiver according to claim 3, further comprising a winding with a switching tap for feeding power to the horizontal deflection circuit and a winding for feeding power to each circuit of the television receiver on the next side. 5. The television according to claim 1, wherein the circuit for obtaining the constant voltage rectified output comprises a voltage doubler rectifier circuit configured to be switchable to a half-wave rectifier circuit, and a continuously controlled constant voltage circuit that receives the output as input. Jiyoung receiver. 6. The television according to claim 1, wherein the horizontal deflection circuit is configured such that the retrace period of the deflection output signal is substantially constant for each television signal having a different horizontal deflection frequency. receiver. 7. The television receiver according to claim 6, wherein the horizontal deflection circuit has an S-shaped correction capacitor connected in series with the horizontal deflection coil and is switched in accordance with the horizontal deflection frequency.