JPH083108Y2 - Adjustment circuit of color television receiver - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial field of application) This invention applies contrast and white balance adjustment to each amplifier circuit that amplifies R (red), G (green), and B (blue) signals. The present invention relates to an adjusting circuit for a color television receiver which is adapted to supply a gain control voltage which also serves as a gain control voltage.

(Prior Art) In a CRT display device such as a color television receiver, a gain control voltage adjusted to a predetermined ratio is supplied to a video amplification circuit that amplifies each R, G, B signal as a white balance adjustment circuit. There is a circuit to supply each.

FIG. 2 shows an example of a conventional adjusting circuit for supplying the gain control voltage, and the structure will be described first. In FIG.
Reference numeral 1 is a variable resistor for white balance adjustment, 5 is a base-grounded transistor for deriving the gain control voltage from a collector, 15 is a variable resistor for contrast adjustment for generating a contrast control voltage, and 20 is a color picture tube. , A voltage source terminal, 21 is a voltage source terminal, and 21 is a common terminal commonly connected to the same terminal of two other circuits (not shown) for guiding the contrast control voltage. .

A diode is connected between the voltage source terminal 19 and the brightness detection terminal 20.
A parallel circuit composed of 17 and a capacitor 18 is connected.
The brightness detection terminal 20 is connected to the base of the transistor 14. The transistor 14 has a collector connected to the voltage source terminal 19, and an emitter connected to the reference potential point through the series connection of the variable resistor 15 and the resistor 16. The output end (sliding end) of the variable resistor 15 is connected to the base of the transistor 13. The collector of the transistor 13 is connected to the reference potential point, and the emitter is connected to the common terminal 21 and the voltage source terminal 19 via the resistor 10.

The common terminal 21 is connected to the emitter of the transistor 5 via the variable resistor 9 and the resistor 4. The base of the transistor 5 is connected to the voltage source terminal 19 via the resistor 8 and is connected to the reference potential point via the series connection of the diode 11 and the constant voltage diode 12. The collector of the transistor 5 is connected to a reference potential point via a resistor 7 and is also connected to a gain control terminal 6 for guiding the gain control voltage to a predetermined video amplifier circuit. The emitter of the transistor 5 is connected to the voltage source terminal 19 via the resistor 3 and to the output end (sliding end) of the variable resistor 1 via the resistor 2. The variable resistor 1 has one end connected to the reference potential point and the other end connected to the voltage source terminal 19.

The circuit with the above configuration is composed of transistors 13, 14, variable resistor 15
The circuit by etc. constitutes the contrast adjustment circuit, and terminal 20
The voltage appearing at is derived from the base of the transistor 14 to the emitter and is varied by the variable resistor 15. Further, the transistor 13 guides a voltage, which is changed opposite to the change of the output terminal voltage of the variable resistor 15, from the emitter to the common terminal 21.

The brightness detection voltage supplied to the terminal 20 is a voltage that changes following the anode current of the color picture tube, and the brightness detection voltage is high when the anode current is small, and the brightness detection voltage is high when the anode current is large. It is decreasing in inverse proportion to it. For example, when the brightness level is in the steady range, the anode current of the picture tube is small and the brightness detection voltage is high, but as the brightness level increases, the anode current of the picture tube increases and the brightness detection voltage decreases.

When the brightness level is in the steady range, the brightness detection voltage supplied to the terminal 20 has a high value, and the diode 17 conducts because the anode voltage is higher than the cathode voltage. Therefore, a constant voltage is applied to the base of the transistor 14 from the voltage source terminal 19, and the contrast control voltage (voltage of the terminal 21) set by the adjustment of the variable resistor 15 does not depend on the brightness level.

On the other hand, if the brightness level becomes higher than the specified value,
Since the brightness detection voltage of 20 decreases, the anode voltage of the diode 17 becomes lower than the cathode voltage and becomes non-conductive, the base of the transistor 14 is disconnected from the voltage source terminal 19, and the base voltage of the transistor 14 becomes 20. It decreases according to the brightness detection voltage of. As a result, the emitter voltage of the transistor 14 also decreases, and the contrast control voltage (voltage at the terminal 21) set by adjusting the variable resistor 15 also decreases, which acts to reduce the contrast.

Now, the circuit including the variable resistor 9, the transistor 5, the variable resistor 1, the constant voltage diode 12 and the like is a gain control voltage generating circuit provided corresponding to each video amplifier circuit.
In this circuit, the electric potential of the common terminal 21 becomes higher than the emitter electric potential of the transistor 5 in a steady state, so that a current flows from the variable resistor 9 to the resistor 4 and the operating current of the transistor 5 is biased to the constant voltage diode 12. It is more than the voltage alone. The increased current can be varied by the variable resistor 9, so that the gain of the transistor 5 is adjusted by the variable resistor 9, and the operation of the transistor 5 around the operating point of the variable resistor 1 is performed. The range can be changed by adjusting the variable resistor 9, whereby the variable gain range of each R, G, B video amplifier circuit is set independently, and the white balance is adjusted even if the contrast control voltage is variably adjusted. The gain control voltage that does not break down is supplied to each of the video amplifier circuits.

On the other hand, when the brightness is limited, the potential of the common terminal 21 becomes lower than the emitter potential of the transistor 5, and a current flows from the resistor 4 to the variable resistor 9. For this reason, the operating current of the transistor 5 is bypassed and decreases from the steady state, the voltage appearing at the terminal 6 falls below the level range exhibited in the steady state, and the gain of each video amplifier circuit is limited to increase the beam current. It suppresses the high brightness state.

By the way, in the circuit of FIG. 2, when the white balance is adjusted, first the adjustment of the variable resistor 1 is performed, but in this case, there is no inflow or outflow of current from the series circuit of the resistor 4 and the variable resistor 9. In this case, the collector voltage of the transistor 5 can be determined only by the variable resistor 1, which results in a good quality adjustment. However, the circuit of FIG. 2 requires accurate adjustment because current flows in the series circuit of the resistor 4 and the variable resistor 9 both when the transistor 13 is off and when it is on. I couldn't. For this reason, there is a drawback in that the white balance does not end once and the adjustment time is long.

(Problems to be Solved by the Invention) In the adjustment circuit shown in FIG. 2, when the operating point of the transistor 5 is adjusted by the variable resistor 1, the variable resistor 9
In addition, since the inflow and outflow of the current through the series circuit of the resistor 4 cannot be prevented, there is a problem that a high-quality adjustment cannot be performed in a short time.

An object of the present invention is to eliminate the above problems and to provide an adjusting circuit of a color television receiver without mutual interference between variable resistors.

[Structure of Device] (Means for Solving the Problem) This device is to supply R (red), G to a color picture tube.
A regulator circuit for supplying a gain control voltage for contrast and white balance adjustment to each amplifier circuit that amplifies the (green) and B (blue) signals, and the emitter-collector current path is at a first potential point. A first circuit connected between the reference potential points, having a base connected to a constant voltage bias source, and including a first transistor adapted to extract the gain control voltage from a collector; and an emitter of the first transistor. Means for supplying a first adjustable voltage for white balance, a brightness detection terminal to which a brightness detection voltage varying according to the brightness level of the picture tube is supplied, and a collector-emitter current path having a first potential point And a reference potential point, a base is connected to the brightness detection terminal, and a first variable resistor for contrast adjustment is connected to the emitter current path, a second transistor. , The emitter
A third transistor configured such that a collector current path is connected between the first potential point and the reference potential point, a voltage adjusted by the first variable resistor is supplied to the base, and a contrast control voltage is taken out from the emitter. A second circuit including: and a base of the first transistor and a base of the second transistor, the brightness level of the second transistor being turned on within a predetermined range. The voltage from the constant voltage bias source is supplied to the base, and when the brightness level changes beyond a predetermined range, the base is turned off and the base voltage of the second transistor is controlled by the brightness detection voltage. And a diode element disposed between the emitter of the first transistor and the emitter of the third transistor. And adjustable means including a second variable resistor that enables adjusting the operating current of the transistor, there the diode element into a conductive state, and the first
When the base voltage of the third transistor is in a state of being equal to the emitter voltage of the second transistor by adjusting the variable resistor of, the emitter voltage of the first transistor and the emitter voltage of the third transistor are equal to each other. 1, a means for biasing the third transistor, and a means for biasing the third transistor.

(Operation) According to the present invention, the diode element is in a conductive state, and the third variable resistor is adjusted to adjust the third variable element.
When the base voltage of the second transistor is equal to the emitter voltage of the second transistor (when the contrast control voltage is maximum), the first and third transistors are biased so that the respective emitter voltages are equal. Therefore, no current flows through the second variable resistor, and the white balance can be easily adjusted by the first variable resistor.

(Embodiment) Hereinafter, the present invention will be described with reference to an illustrated embodiment. FIG. 1 shows an embodiment of an adjusting circuit of a color television receiver according to the present invention.

The circuit of FIG. 1 corresponds to the diode 17 in the circuit of FIG.
The cathode of is connected to the base of the transistor 5 instead of the voltage source terminal 19. The other configurations are the same as those shown in FIG. That is, in FIG. 1, the first adjustable element 51 corresponds to the variable resistor 1, the second adjustable element 59 is the variable resistor 9, the transistor 55 is 5, and the terminal 56 is the gain control terminal 6. And the resistor 52 is 2
The resistor 53 corresponds to 3, the resistor 57 corresponds to 7, the resistor 58 corresponds to 8, the diode 61 corresponds to 11, and the constant voltage diode 62 corresponds to 12.

On the other hand, the circuit inside the dotted line is the contrast adjustment circuit,
Luminance detection terminal 70 to terminal 20, voltage source terminal 69 to terminal 19,
Diode 67 is 17, capacitor 68 is 18, transistor 64 is 14, variable resistor 65 is 15, resistor 66 is 16, transistor 63 is 13, resistor 60 is 10, and common terminal 71 is terminal 21.
Respectively.

The operation of the circuit configured as described above will be described separately in the steady state, the luminance limit, and the adjustment.

Constant In a steady state, the brightness detection voltage introduced to the brightness detection terminal 70 fluctuates in response to the anode current of the color picture tube. At this time, the brightness detection voltage fluctuates within a range sufficiently higher than the output voltage (base voltage VB of the transistor 55) of the constant voltage bias circuit formed by the constant voltage diode 62 and the diode 61, so that the diode 67 is conducting. . Therefore, the base potential of the transistor 64 has a value (VB + VF) higher than the base voltage VB of the transistor 55 by the forward voltage VF of the diode 67, and the emitter of the transistor 64 has a base potential of the transistor 64 higher than that of the base potential VB. A voltage as low as the emitter-to-emitter voltage VBE appears. Although this voltage has a difference between the power supply voltage and the Zener voltage as compared with the case of the circuit of FIG. 2, both are stable voltages that do not fluctuate, and the contrast control voltage is formed by adjusting the variable resistor 65. Become.

The operating current of the transistor 63 is variable according to the contrast control voltage, but in the steady state, the common terminal
Since the potential of 71 is never lower than the emitter potential of the transistor 55, the transistor 55 is the second adjustable element.
As the gain control voltage supplied from the terminal 56 to each video amplifier circuit through the operating current flowing through the resistor 59 and the resistor 54, a voltage higher than that at the time of luminance limitation is supplied. This gain control voltage is adjusted by the first and second adjustable elements 51 and 59, and becomes an independently set voltage adjusted for white balance in each video amplifier circuit.

At the time of brightness limitation When the brightness level increases, the anode current of the color picture tube increases, so the brightness detection voltage at the terminal 70 decreases as the picture tube anode current increases. Therefore, the anode voltage of the diode 67 is its cathode voltage (transistor
It becomes lower than the base voltage VB of 55) and becomes non-conductive. For this reason, the base voltage of the transistor 64 is controlled by the brightness detection voltage applied to the terminal 70, so that the emitter voltage of the transistor 64 decreases and the contrast control voltage decreases from the steady state to deepen the base-emitter bias of the transistor 63. . Therefore, the potential of the common terminal 71 is
Lower than the emitter voltage of the transistor 55 and the operating current of the transistor 55 is shunted through the resistor 54 and the second adjustable element 59,
The gain control voltage from the terminal 56 becomes lower than in the steady state, and the increase in the brightness level can be suppressed.

In this way, this circuit operates in the same manner as the circuit of FIG. 2 both in the steady state and when the brightness is limited.

 Next, the operation at the time of adjustment will be described.

To adjust the white balance, first adjust the first adjustable element.
The operating point of the transistor 55 is set by 51. In the case of this circuit configuration, for example, when the output voltage of the variable resistor 65 is maximized while the diode 67 is conducting (when the mover of the variable resistor 65 is on the emitter side of the transistor 64). , The emitter potential VE1 of the transistor 63 and the emitter potential VE2 of the transistor 55 are almost equal. Because the base potential of the transistor 55 is VB, the diode 6
When the forward voltage of 7 is VF, VE1 = VB + VF (1) Also, the base-emitter voltage of the transistor 55 is VB
Let E be VE2 = VB + VBE (2), and from VBE-VF, VE1 = VE2 (3) From this equation (3), if the output terminal voltage of the variable resistor 65 is set to the maximum level, the resistance 54 and No current flows in the series circuit of the second adjustable element 59, which is the same as if they were separated from the emitter of the transistor 55. Therefore, the first adjustable element 51 can adjust the operating point of the transistor 55 without being affected by the second adjustable element 59. If the first adjustable element 51 is accurately adjusted, the second adjustable element 59 can be easily adjusted,
The white balance can be adjusted without being influenced by the resistance value of each other.

The above embodiment is an example, and as other embodiments, various modifications can be made without departing from the scope of claims for utility model registration.

[Advantages of the Invention] As described above, according to the present invention, mutual interference of a plurality of adjustable elements for adjusting the white balance can be eliminated, and the adjustment becomes easy.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an adjusting circuit of a color television receiver according to the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional adjusting circuit. 51 …… first adjustable element, 53,57,58,60 …… resistor, 55…
… Transistor (gain control voltage forming circuit), 56 …… Gain control terminal, 59 …… Second adjustable element, 63,64 …… Transistor (contrast adjusting circuit), 67 …… Diode,
70 …… Brightness detection terminal, 71 …… Common terminal.

Claims (1)

[Scope of utility model registration request] 1. R (red), G supplied to a color picture tube
A regulator circuit for supplying a gain control voltage for contrast and white balance adjustment to each amplifier circuit that amplifies the (green) and B (blue) signals, and the emitter-collector current path is at a first potential point. It is connected between the reference potential points, the base is connected to the constant voltage bias source,
First to take out the gain control voltage from the collector
A first circuit including a transistor, a means for supplying a first adjustable voltage for white balance to the emitter of the first transistor, and a brightness detection voltage that changes according to the brightness level of the picture tube. A supplied luminance detection terminal, a collector-emitter current path is connected between a first potential point and a reference potential point, and a base is connected to the luminance detection terminal,
A second transistor in which a first variable resistor for contrast adjustment is connected to the emitter current path, and an emitter-collector current path is connected between the first potential point and the reference potential point,
A second circuit having a base to which a voltage adjusted by the first variable resistor is supplied, and a third transistor adapted to extract a contrast control voltage from an emitter; and a base of the first transistor. It is arranged between the base of the second transistor and the brightness level is turned on within a predetermined range to supply the voltage from the constant voltage bias source to the base of the second transistor. A diode element that is rendered non-conductive when the change exceeds a predetermined range so that the base voltage of the second transistor is controlled by the brightness detection voltage, the emitter of the first transistor, and the third transistor. A second variable resistor arranged between the emitter of the second transistor and the emitter of the first transistor, which makes it possible to adjust the operating current amount of the first transistor. And the diode element is in a conductive state, and the base voltage of the third transistor is equal to the emitter voltage of the second transistor by adjusting the first variable resistor. At this time, means for biasing the first and third transistors so that the emitter voltages of the first and third transistors are equal to each other, and an adjusting circuit for a color television receiver.