DE1963820A1 - Circuit arrangement for adjusting the phase of a PAL switch - Google Patents

Description

DipL-lng. ERICH E. WALTHER

Porsnfanwalf 1 Q R? 8th ? Π

Applicant: Philips Faicm.VcrwjIfcng GmbH. ■ '

Akter PHD- 1440
Registration dated: December 18, 1969

PHILIPS PATENTVERWALTüirG GMBH., 2. HAMBURG T, MUM) KEBERGSTR.

"Circuit arrangement for adjusting the phase of a PAL holder".

The invention relates to a circuit arrangement for Adjusting the phase of one that changes at half the line frequency (PAL) switch that is stopped when a DC voltage indicating an incorrect phase position occurs.

With a circuit of this type, even if the phase position is incorrect and a DC voltage occurs when the changeover switch is at a standstill, which permanently stops the switch; the transition to the correct operation is then prevented.

This can be avoided in a simple manner if, according to the Invention to the output circuit of the changeover switch one in the stopped State occurring DC voltage is fed via a delay element to the input in the sense of a feedback. This ensures that the changeover switch resumes its periodic operation, after which the feedback Control variable no longer applies and the normal correction circuit takes effect.

The invention is illustrated below with reference to the drawing, for example explained in more detail.

Color sync signals are sent from input terminals 1 and 2

105826/0707

of opposite polarity via coupling capacitors 3 and 4 of 4.7 nF to the series connection of two resistors 5 and 6 of 100 kJV each and also to the series connection of two diodes 7 and 8. From a terminal 9, 0.1 / uF reference signals of the local color carrier oscillator are fed via a coupling capacitor 10, the phase position of which is switched at half the line frequency in such a way that the color carrier phase discriminator formed in this way at the connection point of the resistors 5 and 6 with respect to the With the connection point of the diodes 7 and 8 W connected to earth, a direct voltage occurs, the polarity of which depends on whether or not the switching of the color sync signal given by the transmitter corresponds to the switching of the oscillator signal for terminal 9 effected in the receiver. If they match, there is a negative voltage at an output capacitor 11 of 0.1 / uF, which blocks an npn transistor 13 via a series resistor 12 of 47 k-fl.

With two nph transistors 14 and 15, a periodic switch (multivibrator) is formed in a manner known per se. In this case, via a network and feed section 16, the Collector and base electrodes in a suitable manner with simple fc connected to the other, and normally the emitters are galvanically connected and connected to the other pole of the supply source, especially earth. Through the network

"- ■ •" .Γ ·: ί '"Tv -

The · Multivibrat then generates the feedback caused by the plant or 14, 15, 16 square waves of the desired frequency, which can also be synchronized from the outside. The collector of transistor 13 is connected to the base of the Transistor 14 connected. If by a positive base DC voltage the transistor 13 is strongly opened, its collector voltage drops sharply so that the transistor locked and thereby the multivibrator stopped for a short time will. This sets the correct phase position. and the opening voltage of the transistor 13 drops out, so

109826/0707 - 3 -

BATH ORIGINAL

that this is blocked. Then the multivibrator runs undisturbed continue. ■ ·.

However, if the phase position of the "reference signal from the terminal 9 deviates significantly from the setpoint, can also be done when the machine is at a standstill Multivibrator, so without determining the phase position, two between the switching of the color sync signal and the receiver-side switching with half the line frequency, a DC voltage occur across the capacitor 11, which the Transistor 13 opens continuously and thus the multivibrator 14, 15, 16 stops.

The emitters of the transistors are therefore in accordance with the invention and 15 not galvanically connected, but via a large one Capacitor 19 of e.g. 10 / UF; every emitter is as well via a resistor 20 or 21 of ΙΟΟΛ. grounded. In normal. Both transistors 14 and 15 are operating alternately open for about the same length such that the mean DC voltage across the two resistors 20 and 21 is about 0.9 volts and there is practically no voltage across the capacitor 19. When stopping briefly to correct the phase, changes to this ratio nothing: the emitters of both transistors 14 and 15 remain at about the same voltage, even if no current flows through the emitter resistor 20 for a while,

V.'enn, however, in the case of the malfunction mentioned, a longer-lasting DC voltage occurs across the capacitor 11 and across the Transistor 13, the transistor 14 is blocked, the capacitor 19 is reloaded in such a way that its with the resistor 20 connected coating becomes more negative and its coating connected to resistor 21 becomes more positive. ,

The emitter of transistor 13 is with the emitter of the transistor 15 connected, and the emitter of transistor 14 is via an isolating resistor 22 of e.g. 22 kJT, with the

109826/0707.,.:, ''"_ _A

BATHROOM ORIGINAL

connection point of diodes 7 and 8 and thus with the base of .Transistor 13 connected. If now through that mentioned disturbing DC voltage of the multivibrator 14 »15» 16 longer Time is stopped, the capacitor 19 charges up and provides a "negative base-emitter voltage for the transistor 13 such that it is blocked and the multivibrator is restarted. This now results in another Changeover of the reference signal supplied to terminal 9 and any phase errors of the reference oscillator become ineffective, so that the arrangement is now back to the phase position responds to the Parbsynchronous pulse.

The voltage across the capacitor 19 thus acts as a temporary one effective feedback or Ire activation of the Multivibrators; this principle can obviously also be implemented with other circuit means.

PATENT CLAIMS:

109826/0707 " ⁵ "

ORfGfPiAL

Claims (3)

PAO) DEFENSE: Circuit arrangement for adjusting the phase of a changing with half the line frequency (PAL- ^ switch, ' which is stopped when a DC voltage indicating an incorrect phase position occurs, characterized in that from the output circuit of the switch (14, 15 * 16) a DC voltage occurring in the stopped state via a delay element fed to the input in the sense of a feedback will. 2. Circuit arrangement according to Claim 1, in which the switch contains two transistors which can be used on the emitter side for the oscillations, characterized in that the emitters. Via a 'capacitor "^ T9) -' y0rbijnd0 ^ $ iM- _; " ti-iid.vdi.e -.-. 4 »in the stationary state, the direct voltage occurring on it is fed to the then blocked transistor (14) in the opening sense, 3. Circuit arrangement according to claim 2, characterized in that "-" indicates that the capacitor ^{voltage controls an upstream stage (tear reservoir:} ϊ3). BATH 109826/07 07 2i η 7 9-44 AG ?; December 19, 1969 OT: June 24th, 1971 109826/0707