JPS5834844Y2 - phase comparison circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase comparator circuit, and more particularly to the same circuit that uses a sawtooth wave voltage as a voltage waveform for comparison and compares it with a reference signal to obtain a control voltage.

Generally automatic frequency control (AFC) in television receivers
When automatically controlling the oscillation frequency of a horizontal oscillation circuit such as in a circuit, simply fix one base of the differential pair transistor to a potential divided by a voltage dividing resistor, and connect the other base with a sawtooth shape for comparison. wave voltage (Fig. 3 A) is applied, and a horizontal synchronizing signal (Fig. 3 A) serving as a reference signal is applied to the switching transistor connected to the common emitter of the differential pair transistors. The configuration is such that the control voltage is derived from the collector of the transistor, and the comparison is performed at the DC level VDO of the sawtooth wave voltage for comparison, and the phase comparison time cannot be changed.

Therefore, the present invention provides a novel phase comparator circuit in which the phase time can be changed in size depending on design specifications.

Next, the present invention will be explained with reference to the drawings. FIG. 1 shows one embodiment of the circuit of the present invention, and FIG. 2 shows another embodiment of the same circuit. First, FIG. 1 will be explained.

In FIG. 1, 1 is a comparison voltage terminal to which a sawtooth wave voltage for comparison is applied, 2 is a reference signal application terminal, 1 is a comparator consisting of differential pair transistors 4 and 5, 6 is a first switching transistor, and 7 1 is a voltage dividing circuit consisting of a first voltage dividing resistor 8, a second voltage dividing resistor 9, and a third voltage dividing resistor 10; 11 is a second switching transistor; 12 is a load transistor;
indicates an output terminal, and 14 indicates a flyback pulse application terminal.

To explain the operation of FIG. 1, the sawtooth wave voltage Vs for comparison is applied to the terminal 1, and the horizontal synchronizing signal vH
, the first switching transistor 6 is turned on and the emitter potentials of the differential pair transistors 4 and 5 are lowered, causing the sawtooth wave voltage Vs with respect to the horizontal synchronizing signal VH.
Performs a phase comparison.

In this case, a flyback pulse is applied to terminal 14, so
The second switching transistor 11 is turned on, and the third switching transistor 11 is turned on.
Both ends of the resistor 10 are short-circuited at the collector-emitter path of the transistor 11, the base potential of the differential pair transistor 5 as a reference voltage is lowered as shown in FIG. 4A, and the phase comparison time T1 is shorter than T in the conventional circuit. It is set to a small value, that is, T1×T.

Next, referring to FIG. 2, the collector-emitter path of the second switching transistor 11 is connected to both ends of the first resistor 8;
The output side of the third switching transistor 15 is connected to the base of the third switching transistor 15, and the flyback pulse applied to the terminal 14 causes the third switching transistor 1 to
5 is turned on and the second switching transistor 11 is turned on, the base potential of the differential pair transistor 5 rises as shown in FIG. is set to

As described above, according to the present invention, as shown in the embodiment of FIG. 1 or 2, by changing the base potential of one of the differential pair transistors constituting the comparator during the flyback period, The time can be set arbitrarily, and a phase comparator circuit can be provided according to the design specifications.Since the present invention has a simple configuration, it is easy to integrate it into an integrated circuit (IC) and is extremely suitable for AFC circuits of television receivers. Useful.

[Brief explanation of drawings]

Figures 1 and 2 show the phase comparator circuit of the present invention, Figure 3 A2
Figures 4 and 5 are explanatory waveform diagrams of the conventional circuit, respectively.
Figure A2 shows an explanatory waveform diagram of the same circuit of the present invention. Explanation of main figure numbers, 1... Comparison voltage terminal, 2... Reference signal application terminal, 3... Comparator, 4, 5... Differential pair transistor, 6... First switching transistor,
-1-... Voltage dividing circuit, 11... Second switching transistor.

Claims (1)

[Scope of utility model registration request] One base side of the differential pair transistors is connected to a comparison voltage terminal to which a comparison sawtooth wave voltage is applied, and the other base side of the differential pair transistors is sequentially connected between the power supply and the reference potential point. 1st, 2nd. The base side of the first switching transistor is connected to one voltage dividing point of the voltage dividing circuit consisting of the third resistor, and the collector-emitter is connected between the common emitter of the differential pair transistors and the reference potential point. A terminal for applying a flyback pulse is connected to a reference signal application terminal to which a horizontal synchronizing signal is applied, and a terminal for applying a flyback pulse is connected to the base side of a second switching transistor whose collector and emitter are connected in parallel to the first resistor or the third resistor. connection,
A phase comparison circuit characterized in that an output terminal is connected to the collector of one of the differential pair transistors.