JP2001309400A - Integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated circuit to be used in the case of outputting a video signal such as a luminance signal, a chrominance signal or a composite signal to a video appliance. SOLUTION: The integrated circuit to be used in the case of outputting the video signal to the video appliance incorporates a negative power source generation means for generating a negative power source by using a supplied positive power source and has an output driver for outputting the video signal by DC combination energized by the positive power source and the negative power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an integrated circuit used for outputting a video signal such as a luminance signal, a chrominance signal, or a composite signal to a video device.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration in which a video signal VS1 is input.
This shows a first configuration example of a conventional output driver 21 that operates with a single power supply that outputs this as a 75Ω video signal VS2 to a video device 20 such as a television or a video recorder.

The base of the transistor Q1 has a positive power supply V
A divided voltage divided by resistors R1 and R2 is applied between CC and ground GND, and input terminals T1 and T
2, a video signal VS1 is input.

A positive power supply V is applied to the collector of the transistor Q1.
CC is applied, the emitter is connected to the ground GND via the resistor R3, and further from the emitter to the output terminals T3 and T4 via the series circuit of the resistor R4 and the coupling capacitor C1, corresponding to the video signal VS1. The video signal VS2 is output.

The resistors R1 and R2 and the transistor Q1 can be integrated into an integrated circuit. However, since the resistor R3 generates a large amount of heat when incorporated in the integrated circuit, it is generally externally mounted.

In this case, the resistances of the resistors R4 and R5 are 75Ω.
And the coupling capacitor C1 is 470 μF
１０００1000 μF, and the emitter current IE is A
Class operation, a current of about 20 mA is designed to flow at all times. Generally, the resistor R4 and the coupling capacitor C1 are large and are externally mounted.

The output terminal T3 of the output driver 21
And T4, and the input terminals T5 and T6 of the video device 20 are connected by a connection cable 22, and the input terminal T on the receiving side is connected.
Between 5 and T6, a video signal VS2 is inputted as being terminated by a resistor R5 as an input resistor.

With such a configuration, the video signal VS1
The DC signal is cut off by the coupling capacitor C1 of the output driver 21, amplified if necessary, the output impedance is set to 75Ω, and the video signal VS
Output as 2.

As described above, in the conventional output driver 21 which operates with a single power supply, the emitter current IE always flows about 20 mA per system, so that the power consumption is about 200 mW per system.

The DC component is cut by the coupling capacitor C1 due to the potential difference between the receiving end and the output end.
Since a low-frequency signal has to be passed, 470 μF to 100 determined by the allowable amount of sag on the video device 20 side
A large capacitor of 0 μF is required.

As described above, since the power consumption is large, it is difficult to form an integrated circuit as a whole. However, since the circuit is simple, there is an advantage that it can be performed at a relatively low cost. The circuit is configured as follows.

An improvement in this point is a feedback type 75Ω driver shown in FIG. 6 as a second configuration example. In this case, the output driver 23 has input terminals T7 and T7.
8, output terminals T9 and T10 are provided, and input terminal T7
Between the non-inverting input terminal (+) of the amplifier Q2 of 6 dB, the driver Q3, the capacitor C2, and the resistor R
4 (= 75Ω) are connected in cascade.

Then, a negative feedback is made from the connection point between the coupling capacitor C2 and the resistor R4 to the inverting input terminal (-) of the amplifier Q2 via the capacitor C3, and the input terminal T8 and the output terminal T10 are connected as the ground GND. Thus, a video signal VS3 is obtained between the output terminals T9 and T10. In this case, the capacitors C2 and C3 and the resistor R4 are generally externally connected.

According to such a configuration, power consumption can be reduced, but the capacitors C2 and C3
Is required, and the capacitor C3 is 22 μF
However, the capacitor C2 still needs to be about 220 μF to 470 μF in order to suppress the sag. However, at present, since a single power supply of about 5 volts can be used, an integrated circuit of this type is often used.

In the third configuration example, a driver of a dual power supply system is generally used, and these disadvantages are eliminated. However, since there is a problem that a positive and negative power supply must be prepared, the cost is reduced. Although this is not so advantageous as compared with the feedback system in terms of the occupied area, it is an effective system when there are two positive and negative power supplies that can be used.

The use of two power supplies simplifies the circuit configuration and requires one less terminal than the feedback system, so this terminal can be used as a guard and the amount of crosstalk between output systems can be reduced. be able to.

This point is advantageous in that a signal driver of a video device which requires three signals, a luminance signal, a chrominance signal, a composite signal and a component signal, requires a small package and a small number of electrolytic capacitors. .

[0018]

However, in the above-mentioned first configuration example, there is a problem that a large coupling capacitor is required, power consumption is large, and it is difficult to form an integrated circuit. Compared to the configuration example, a small capacitor is sufficient, but there is a problem that two capacitors are required and a large capacitor is still required. Further, in the third configuration example, two positive and negative power supplies must be prepared. There's a problem.

[0019]

According to the present invention, there is provided an integrated circuit for use in outputting a video signal to a video device as a configuration of an integrated circuit for solving the above problems.
A negative power supply generating means for generating a negative power supply using the supplied positive power supply, and an output driver energized by the positive power supply and the negative power supply and outputting the video signal by DC coupling; is there.

Since the present invention has the negative power supply generating means, the output driver is constituted by adopting a simple circuit configuration as in the case where there is both the positive and negative power supplies without the use of the positive and negative power supplies. In addition, since no coupling capacitor is required, the cost can be substantially saved only by the integrated circuit, and the integrated circuit can be reduced in size by the simple circuit configuration, so that the area occupied by the substrate can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an integrated circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram schematically showing one embodiment of the present invention. Note that components having the same functions as those in the related art are denoted by the same reference numerals for easy understanding, and description thereof is omitted.

As shown in FIG. 1, the integrated circuit 25 is roughly divided into a charge pump boost functioning as a negative power supply generating means for receiving a power supply from a positive power supply VCC supplied to the terminal 16 and generating a negative power supply. It comprises a circuit 26 and a signal drive circuit 27 which is a circuit part other than the charge pump boost circuit 26.

The charge pump boost circuit 26 uses the positive power supply VCC from the terminal 16 to generate a negative voltage OUT at the terminal 17 with respect to the ground GND shown at the terminals 6, 10, and 14. as,
For example, there is about 10 mA (peak) per driver system, and if this capability is increased, it is possible to drive two loads with the same output.

In this case, although this negative voltage OUT is not shown, it is output as it is as a negative power supply VEE to the terminal 7, and a noise suppression circuit having a configuration described later for the negative voltage OUT generated at the terminal 17. In some cases, the noise is removed at 28 and then output to the terminal 7. In any case, the negative power supply VEE at the terminal 7 is used by the internal signal drive circuit 27.

The charge pump boost circuit 26 uses an inverting capacitor C4 or the like in the process of converting a positive voltage to a negative voltage. When the capacitance is small, the capacitor C4 is used with no polarity. In some cases, a polar capacitor such as a capacitor is used. In this case, the terminal 8 is externally connected to the positive side as C4 +, and the terminal 9 is externally connected to the negative side as C4-. These capacitors are connected as necessary.

The other circuits are the signal drive circuit 27
However, at the input end of the signal drive circuit 27, the terminal 1 receives the luminance signal Y-IN, the terminal 5 receives the chrominance signal C-IN, and the terminal 3 receives the composite signal COMP-I.
N is a mute signal MUT at terminal 2 as a control signal.
E and the amplified signal AMP at the terminal 4 are input.

On the output side of the signal drive circuit 27, the terminal 15 receives the luminance signal Y-OUT and the terminal 11
The terminal 13 has a luminance signal Y-I.
A composite signal CO obtained by mixing N and the color signal C-IN
MP-OUT are output, and a composite signal COMP-IN and a luminance signal Y-IN are used as control signals.
And a mix signal YC-MIX for switching between an addition signal Y / C obtained by adding the color signal C-IN and the color signal C-IN.

The luminance signal Y-IN input to the terminal 1 is
The signal is filtered by an input filter circuit 29 described later, and is applied to one end (●) of the switching end of the switch SW1 in which the ground voltage is applied to the other end (○) of the normally open switching end, and is applied via the common end. Output to the amplifier 30.

The amplifier 30 having a high input impedance is energized by the positive power supply VCC and the negative power supply VEE generated by the charge pump boost circuit 26, and amplifies the signal obtained from the common terminal of the switch SW1 by, for example, 6 dB. One end (●) of the switching end is applied to the other end (○) of the switching end of the switch SW2 connected to the common end of the switch SW1.

The common terminal of the switch SW2 is applied to an input terminal of an output driver 31, which will be described later, and has a positive power supply VCC and a negative power supply VEE generated by the charge pump boost circuit 26.
The output driver 31 energized at this time outputs the luminance signal Y-I so as to enable DC coupling with the video device 20 on the load side.
N is converted and output to a terminal 15 as a luminance signal Y-OUT.

The color signal C-IN input to the terminal 5 is filtered by an input filter circuit 29 described later.
Switch SW with ground voltage applied to the other end (他 端) of the switching end
The signal is applied to one end (●) of the switching end of No. 3 and output to the amplifier 32 via the common end.

Amplifier 32 with high input impedance
Is energized by the positive power supply VCC and the negative power supply VEE generated by the charge pump boost circuit 26, and the switch SW3
The signal obtained from the common end of the switch SW3 is amplified, for example, by 6 dB, and one end (●) of the switch end is applied to the other end (○) of the switch end of the switch SW4 connected to the common end of the switch SW3.

A common terminal of the switch SW4 is applied to an input terminal of an output driver 33, which will be described later, and has a positive power supply VCC and a negative power supply VEE generated by the charge pump boost circuit 26.
The output driver 33 energized in the step (c) outputs a color signal C-IN to a signal suitable for DC coupling with the video device 20 on the load side.
And outputs it to the terminal 11 as a color signal C-OUT.

The composite signal CO input to the terminal 3
The MP-IN is filtered by an input filter circuit 29 to be described later, applied to one end (●) of the switching end of the switch SW5 in which the ground voltage is applied to the other end (○) of the switching end, and is applied through the common end. Is output to the amplifier 34.

Amplifier 34 with high input impedance
Is energized by the positive power supply VCC and the negative power supply VEE generated by the charge pump boost circuit 26, and the switch SW5
The signal obtained from the common end of the switch SW6 is amplified by, for example, 6 dB, and one end (●) of the switch end is applied to the other end (○) of the switch end of the switch SW6 connected to the common end of the switch SW5.

The signal at the common end of the switch SW6 is applied to one end (●) of the switching end of the switch SW7,
The MIX circuit 35 adds the luminance signal Y-IN obtained at the common end of the switch SW2 and the color signal C-IN obtained at the common end of the switch SW4 to the other end (他 端) of the switching end of No. 7. The obtained addition signal Y / C is applied.

The addition signal Y / C is applied to an input terminal of an output driver 36 described later, and the output driver 36 energized by the positive power supply VCC and the negative power supply VEE generated by the charge pump boost circuit 26 outputs Here, the composite signal C is converted into a signal suitable for DC coupling with the video equipment 20 on the load side.
OMP-IN is converted and the composite signal C
Output as OMP-OUT.

Mute signal MUTE applied to terminal 2
Is applied to the switches SW1, SW3, or SW5, and these switches are switched and controlled by, for example, one control line to ground a common terminal of these switches, or to output a luminance signal Y-IN and a chrominance signal C-IN. , Or by passing the composite signal COMP-IN,
13 is controlled to output these signals.

When these switches SW1, SW3, or SW5 fall to the other end (○) of the switching terminal by the MUTE signal, the next stage circuit is grounded and the luminance signal Y-IN, the color signal C-IN, or the composite signal is output. The signal COMP-IN is
Muted.

The amplified signal AMP applied to the terminal 4 is applied to the switches SW2, SW4, or SW6, and these switches are switched and controlled by, for example, one control line, and the common terminal of these switches is connected to the amplifier 30, 32 or 3
Control is performed to determine whether the signal is output as a through signal without passing through it, or is amplified by, for example, 6 dB and output through these amplifiers.

If the input level is high and the same as the output level, the signal is set as a through signal, that is, 0 dB. If the input level is low, the signal is amplified by, for example, 6 dB so that the signal processing in the subsequent stage becomes easy.

The mix signal YC-MIX as a control signal applied to the terminal 12 controls the switching of the switch SW7. The control signal includes a luminance signal Y-IN generated by the MIX circuit 35 and a color signal C-IN. Is added to the addition signal Y /
C or the composite signal COMP-I
Selection is made as to whether or not to output N. This is effective for video output of a device such as a video camera that processes a signal system with two systems of a luminance signal Y-IN and a chrominance signal C-IN.

As described above, the integrated circuit 25 has an input filter circuit 29 for removing noise, for example, 6d.
Amplifier 30, 32, or 34 for amplifying B, or MIX for adding luminance signal Y-IN and color signal C-IN
If the circuit 35 and the like are built in, peripheral circuits can be taken in, which is convenient.

The input filter circuit 29 shown in FIG. 1 is configured as a low-pass filter. Although they are listed in 1 above, if they are unclear, they will be externally attached as shown in FIG.

When the input video signal is the output of a DA (Digital / Analog) converter 37 like a recent digital device, the sampling clock and its harmonic components may be present in addition to the required band. If the input signal line is long, noise is superimposed.

In each of these cases, the quality of the signal is degraded. Therefore, as shown in FIG. 2, a filter similar to the input filter circuit 29 is generally used as an input filter circuit 38 configured as a low-pass filter. It is inserted before the terminal 1, 3, or 5 of the signal drive circuit 27. However, FIG. 2 schematically shows only the terminal 1.

In the input filter circuit 38, a resistor R6 and an inductance L1 are connected in series between input and output terminals.
Both ends of the inductance L1 are connected to the ground GND by the capacitors C4 and C5 to form a low-pass filter.

Each of the output drivers 31, 33, and 36 is energized by using the supplied positive power supply VCC and the negative power supply VEE generated by the charge pump boost circuit 26, and has substantially the same configuration. Therefore, the following description will be given based on the output driver 31 and the subsequent stages.

The base is connected to the collector and the emitter of the transistor Q4, whose base is grounded via the resistor R8, via the resistor R7 from the positive power source VCC and the constant current source CC1 from the negative power source VEE.

Further, a positive power supply VCC is applied to the collector of the transistor Q5 whose base is connected to the collector of the transistor Q4, and a negative power supply VEE is applied to its emitter via a constant current source CC2.

A constant current circuit CC3, a diode D1 connected in the forward direction, a diode D2 connected in the forward direction, and a constant current circuit CC4 are provided between the positive power supply VCC and the negative power supply VEE. They are connected in series.

In addition, between the positive power supply VCC and the negative power supply VEE, the collector and the emitter of the transistor Q6 whose base is connected to the connection point between the constant current circuit CC3 and the diode D1, and the base are connected to the diode D2. Current circuit CC4
The emitter and the collector of the transistor Q6 connected to the connection point are connected in series.

The emitters of the transistors Q5 and Q6 are both connected to the terminal 15 and are connected to a terminal 7 for impedance matching.
It is connected to the input terminal of the video device 20 via a 5Ω resistor R4.

In the above configuration, the luminance signal Y-IN is input to the base of the transistor Q4, and the luminance signal Y-IN corresponding to the luminance signal Y-IN is supplied to the output terminal 15.
OUT is output.

In this case, in response to the zero signal of the luminance signal Y-IN, the base of the transistor Q4 is at zero potential, the emitter potential of the transistor Q5 is also zero potential, the emitters of the transistors Q6 and Q7 are also at zero potential. Outputs a zero signal, so that a luminance signal Y-OUT is output as a signal that changes to positive or negative with the zero potential as an operating point.

The voltage VBE between the base and the emitter of the transistors Q4, Q5, Q6, Q7 and the diodes D1, D2
Can be adjusted so that the potential at the output terminal 15 becomes zero when the potential at the base of the transistor Q4 is zero by controlling the current values of the constant current sources CC1 to CC3. .

Generally, 75 Ω is used for transmitting a video signal.
Since a coaxial cable having an impedance of ?? is used, the impedance of transmission and reception is set to 75? And impedance matching is performed.

Since the impedance of 75 Ω is very low, if a signal is transmitted using a coupling capacitor, low-frequency distortion will occur, and a large-capacity capacitor is required to obtain a quality that does not cause any problem. The fundamental solution to the distortion problem is DC coupling without using capacitors.

Therefore, although only the positive power supply VCC is supplied, the negative voltage VEE is generated by the charge pump boost circuit 26 and operated as a dual power supply system, thereby connecting the video equipment 20 with the video equipment 20 by DC coupling. In this way, distortion can be prevented while impedance matching is performed, and the entire package of the integrated circuit 25 can be reduced in size.
It is also possible in SSOP as well as Outline Package).

Since the charge pump boost circuit 26 has an internal oscillation circuit, it may give a noise to a negative power supply or a signal due to this effect, and this noise generally gets on the power supply line. As shown in the figure, the noise suppression circuit 28 is connected between the terminal 17 which is the output terminal of the charge pump boost circuit 26 and the terminal 7 of the negative power supply VEE.

The noise suppression circuit 28 is, specifically,
As shown in FIG. 4, a noise suppression circuit 28 configured as a low-pass filter is inserted between the terminal 17 and the terminal 7.

In the noise suppressing circuit 28, a resistor R9 and an inductance L2 are connected in series between a terminal 17 and a terminal 7, and capacitors C6 and C7 are connected to ground GND from both ends of the resistor R9 and the inductance L2. , C
8, and an electrolytic capacitor C9 is inserted between the terminal 7 and the ground GND.

The integrated circuit 25 is connected to the terminal 7 of the negative voltage VEE generated by the charge pump boost circuit 26.
Therefore, there is an advantage that the cost can be saved and the area occupied by the substrate can be reduced by using the video equipment without a negative power supply as necessary.

In addition, the present integrated circuit can be used without any problem even in a circuit system capable of supplying a dual power supply, since the video buffer circuit has a circuit configuration for the dual power supply. It works like a dual-powered amplifier.

Even if the charge pump boost circuit 26 is incorporated in the integrated circuit 25, the cost as a semiconductor hardly changes, and the present integrated circuit has an advantage that it can be used in a single power supply system or a dual power supply system.

[0066]

As described above, according to the integrated circuit of the present invention, since the integrated circuit has the negative power supply generating means, it is the same as the case where there is both the positive and negative power supplies without the both positive and negative power supplies. The video signal driver can be configured by adopting a simple circuit configuration as described above, and the cost is substantially reduced only by the integrated circuit because no coupling capacitor is required, and the integrated circuit is reduced in size by the simple circuit configuration. Therefore, the area occupied by the substrate can be reduced.

Since a game machine or the like does not require much audio performance, it is constituted by a single power supply. The size of the device is also reduced, and the degree of integration of mounting is increasing. Therefore, the development of small parts is desired. Among them, a small-sized integrated circuit equipped with such a video signal driver can meet the demand.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment according to the present invention.

FIG. 2 is a block diagram showing a configuration near an input filter circuit shown in FIG. 1;

FIG. 3 is a circuit diagram showing a configuration near an output driver shown in FIG. 1;

FIG. 4 is a circuit diagram illustrating a configuration of a noise suppression circuit illustrated in FIG. 1;

FIG. 5 is a first circuit diagram showing a configuration near a conventional output driver.

FIG. 6 is a second circuit diagram showing a configuration near a conventional output driver.

[Explanation of symbols]

20; video equipment, 21; output driver, 22; connection cable, 23; output driver, 25; integrated circuit, 26;
Charge pump boost circuit, 27; signal drive circuit, 28; noise suppression circuit, 29; input filter circuit,
30; amplifier, 31; output driver, 32; amplifier, 3
3; output driver; 34; amplifier; 35; MIX circuit;
36; output driver, 37; DA converter, 38; input filter circuit, Y-IN; luminance signal, C-IN; color signal, COMP-IN; composite signal, Y-OUT;
Luminance signal, C-OUT; color signal, COMP-OUT; composite signal, MUTE; mute signal, YC-MI
X: mix signal, AMP: amplified signal, VEE: negative power supply, VCC: positive power supply

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) AV04 AV05 AZ03 BG05 BG06 BH19 CD14 DF01 DF03 DF17 EZ20

Claims (7)

[Claims] An integrated circuit used for outputting a video signal to a video device, comprising a negative power supply generating means for generating a negative power supply using a supplied positive power supply, wherein the positive power supply and the negative power supply are connected to each other. An integrated circuit comprising an output driver energized by a power supply and outputting the video signal by DC coupling. 2. The integrated circuit according to claim 1, wherein said negative power supply generating means is realized using a charge pump boost circuit. 3. A MIX circuit which receives a luminance signal and a chrominance signal and generates an addition signal obtained by mixing these signals, and switches and outputs the input composite signal and the addition signal. An integrated circuit as described. 4. The integrated circuit according to claim 1, further comprising switching means for switching and outputting an amplified signal obtained by amplifying the input signal by an amplifier and a through signal for outputting the input signal as it is. 5. The integrated circuit according to claim 1, further comprising an internal or external input filter unit to which a video signal is input. 6. The integrated circuit according to claim 2, wherein the charge pump boost circuit includes a noise suppression circuit for suppressing noise between an output terminal of the charge pump boost circuit and a negative power supply terminal. 7. The integrated circuit according to claim 2, wherein the charge pump boost circuit directly outputs an output of the charge pump boost circuit to a negative power supply terminal.