JPH0246112Y2 - - Google Patents

Description

[Detailed description of the invention] The invention provides a first high level pulse having a pulse width narrower than that of the first pulse during a period in which the first pulse is at the first high (or low) level. This relates to a circuit that separates a synthesized pulse into the original first and second pulses from which a second pulse with a second high (or low) level higher (or lower) than the second high (or low) level is superimposed. be.

In particular, when TV receivers in Europe use a pulse in which a gate pulse is superimposed on a blanking pulse (hereinafter referred to as a sandcast pulse) as shown in Figure 2a, this is processed and the blanking pulse and gate pulse are superimposed. A circuit is required to separate the pulses into pulses.

FIG. 1 shows a conventional example of such a pulse separation circuit. Reference numeral 19 denotes a sandcast pulse input terminal, which is connected to the base of the transistor 15 constituting a first comparator circuit consisting of a differential circuit, and also constituting a second comparator circuit consisting of a differential circuit. Connected to the base of transistor 9. The collector of the transistor 15 is grounded, and the emitter is connected to the emitter of the other transistor 14 and to the collector of the constant current transistor 13. The collector of transistor 14 is resistor 17
is grounded through the base, and the base has resistors 1, 3, 4,
5. The first bias obtained is applied to the connection point between the resistors 4 and 5 of the bias source consisting of the diode 2. The emitter of the transistor 13 is connected to the power supply 18 via the resistor 12, and the base is connected to the connection point between the diode 2 of the bias source and the resistor 3. Resistors 1 and 12, diode 2, transistors 7 and 1
3 constitute two current mirror circuits. Also, resistors 6, 11, transistors 7, 8, 9
The second comparator circuit has the same connection configuration as the first comparator circuit, except that the base of transistor 8, which forms a differential circuit with transistor 9, is connected to the second bias and the connection point between resistors 3 and 4. to do.

Next, the operation of this separation circuit will be explained. The threshold and first bias potential of the first comparator circuit are set lower than level A in FIG. 2a, and the threshold and second bias potential of the second comparator circuit are set to level B higher than level A in FIG. 2a. is set lower. When the sandcast pulse is not input, input terminal 19 is in a grounded state, transistors 9 and 15 are conductive, and current from constant current transistors 7 and 13 flows to transistors 9 and 15, respectively. Therefore, nothing is output to the blanking pulse output 16 and the gate pulse output 10. When a sand catastrophe pulse is input, the first comparator circuit is inverted only during the period _t1 during which the level exceeds the first bias potential, the transistor 14 becomes conductive, current flows through the resistor 17, and a blanking pulse is output. 16, the pulse shown in FIG. 2b is obtained. Moreover, the second comparison circuit has a level period t ₂ exceeding the second bias potential.
is inverted, transistor 8 becomes conductive, current flows through resistor 11, and a pulse shown in FIG. 2c is obtained as gate pulse output 10. In this way two pulses are separated from the sandcast pulse.

However, in this conventional isolation circuit, current must always flow through the bias source and the two comparison circuits regardless of the presence or absence of the sandcast pulse. As the integration of television signal processing circuits increases, it becomes imperative to reduce power consumption, and such separation circuits have the disadvantage of wasting power. Further, in order to reduce power consumption, it is possible to increase the resistance value, but this increases the pellet area, which is not preferable.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a pulse separation circuit with low power consumption.

The pulse separation circuit of the present invention includes a constant current source and a pulse width that is narrower than the pulse width of the first pulse during the period in which the first pulse is at the first high (or low) level. input a composite pulse on which a second pulse having a second high (or low) level higher (or lower) than the high (or low) level of a switch means for operating the constant current source; a detection means for detecting the current of the constant current source and outputting the first pulse; and a switch means for detecting the current of the constant current source and outputting the first pulse; (or low) level and comparing means for comparing the synthesized pulse and outputting the second pulse.

FIG. 3 shows an embodiment of the present invention. In FIG. 3, the same parts as in FIG. 1 are designated with the same reference numerals. Sandcastle pulse input terminal 1
9 is connected to the base of transistor 9 and connected to switching transistor 2 via resistor 23.
Connected to the base of 2. The emitter of the transistor 22 is grounded, and the collector is connected via the resistor 21 to the diode 2 and the bases of the constant current transistors 7 and 13. Diode 2 is connected to a power supply via resistor 1, and resistors 1, 6, and 12, diode 2, and transistors 7 and 13 constitute two current mirror circuits. The collector of transistor 13 is grounded via resistor 17. The base of transistor 8 of the comparison circuit having a differential configuration is connected to a bias source 20 having the same potential as a second bias connected to the base of transistor 8 in FIG.

Next, the operation of FIG. 3 will be explained. When the sandcast pulse is not input, the input terminal 19 is in a grounded state, so the transistor 22 is not conductive.
No current flows through resistors 1 and 21 and diode 2, so the two current mirror circuits do not operate.
No output appears at blanking pulse output 16 and gate pulse output 10.

When a sandcast pulse is input, the transistor 22 is conductive only during the input period t ₁ of the sandcast pulse (shown in FIG. 2a), and the resistors 1,
A current flows through the 21 diode 2, and two current mirror circuits operate. Transistor 13 becomes conductive, current flows through resistor 17, and a blanking pulse shown in FIG. 2b is taken out as output 16. Also, the transistor 7 becomes conductive, and the comparison circuit consisting of the resistors 6 and 11 and the transistors 8 and 9 operates, and only the input period _t2 , which is higher than the potential of the bias source 20, is inverted, the transistor 8 becomes conductive, and a current flows through the resistor 11.
The gate pulse shown in FIG. 2c is taken out as output 10. In this way, this separation circuit operates only when the sandcast pulse is input, and the blanking pulse and gate pulse can be extracted respectively.

Further, since the circuit described above uses only one bias source 20, other suitable biases of semiconductor integrated television signal processing circuits can be used.

As described above, according to the present invention, it is not necessary to constantly flow current as in the conventional example, and power consumption can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional pulse separation circuit, Fig. 2 is a waveform diagram for explaining the operation of the circuit in Fig. 1, and Fig. 3 shows an embodiment of the pulse separation circuit of the present invention. It is a circuit diagram. 1, 3, 4, 5, 6, 11, 12, 17, 2
1, 23...Resistor, 2...Diode, 7,8,
9, 13, 14, 15, 22...transistor,
18...Power supply, 19...Pulse input terminal, 20...
...bias source, A, B...pulse level, t ₁ ,
t ₂ ...Pulse input period.

Claims (1)

[Scope of utility model registration request] a constant current source, and during the period when the first pulse is at the first high (or low) level, the pulse width is narrower than the pulse width of the first pulse and is lower than the first high (or low) level. A switch means that receives as input a composite pulse on which a second pulse having a second high (or low) level is superimposed, and operates the constant current source for a period of pulse width of the first pulse. a detection means for detecting the current of the constant current source and outputting the first pulse; and a detection means for detecting the current of the constant current source and outputting the first pulse; A pulse separation circuit comprising: comparison means for comparing a level with the synthetic pulse and outputting the second pulse.