JPH02274069A - Anode voltage adjusting circuit for cathode ray tube - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of a focus point by superposing an output of an adjusting circuit of a differential constitution to a low voltage side terminal for an anode voltage of a secondary side winding. CONSTITUTION:When a power supply voltage +B supplied to a primary side of a fly-back transformer 12 generates an error against a reference voltage value, an anode voltage supplied to a CRT 10 generates an error against a voltage value which is set in the beginning. Therefore, in the case a focus adjustment of the CRT 10 comes off from a set state in the beginning and becomes incorrect, the power supply voltage dependency of resolution is eliminated by canceling an error portion generated in the anode voltage by the influence of an error portion of the power supply voltage +B supplied to the primary side. In such a way, the anode voltage adjusted in the beginning is always in a correct state and an optimum focus point of the CRT 10 can be obtained easily.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an anode voltage adjustment circuit for a cathode ray tube (hereinafter referred to as CRT), and in particular, to eliminate the dependence of the resolution on power supply voltage fluctuations of a magnetic field focusing type CRT. The present invention also relates to a cathode ray tube anode voltage adjustment circuit for obtaining an optimum focus point.

[Conventional technology]

Conventionally, as a magnetic field focusing type CRT, one having an electrode structure consisting of a cathode K, a first grid G3, a second grid G2, and an anode A is known. This kind of CRT
In general, the circuit is configured such that a control signal such as a video signal is input to the first grid G1 and cathode K, and an anode voltage generated in the secondary winding of the flyback transformer is applied to the anode A. For example, on the primary side of a flyback transformer, a horizontal drive pulse is supplied to drive the deflection yoke, and at the same time, the flyback pulse resonated by the resonant capacitor and the deflection yoke during the horizontal retrace period is transferred to the flyback transformer. By supplying the voltage to the primary winding, the circuit can be configured to generate the required anode voltage in the secondary winding.

However, in this type of CRT, in order to keep the high voltage constant, it is generally adopted to apply a horizontal retrace pulse to the low voltage part of the high voltage winding, but in this case, pulses are accumulated to keep the high voltage constant. As a result, the focus voltage coming out from the middle tap of the high-voltage winding tends to fluctuate. Therefore, in this case, in order to obtain the optimum focus point of the CRT, methods have been proposed in which, for example, the width of the flyback voltage by a flyback transformer is varied or the power supply voltage is varied.

[Problem to be solved by the invention]

However, the former method of varying the flyback voltage width generally has the disadvantage that the scale cannot be adjusted smoothly due to the high voltage it handles, and the adjustment range is not sufficient. Furthermore, the latter method of changing the power supply voltage not only causes power loss, but also causes variations in the in-plane dimensions of the CRT, making it impossible to reproduce an appropriate image.

In addition, the flyback pulse obtained on the primary side of the flyback transformer is affected by the deflection yoke, resonant capacitor, flyback transformer, etc., and the pulse width and peak value vary. The high voltage applied to the anode (hereinafter referred to as anode voltage) generated during this process also hardly falls within the tolerance range required for CRTs.

Furthermore, in CRTs for electronic viewfinders used with video cameras, there is some variation in the power supply voltage supplied to the electronic viewfinder from each video camera for focus adjustment. Even if you supply the standard power supply voltage to the viewfinder and adjust the focus with the electronic viewfinder alone, when the electronic viewfinder is actually incorporated into the video camera, the power supply voltage supplied from the video camera will vary to some extent. -The focus point changes without adjustment, resulting in inappropriate resolution, and the focus has to be adjusted again, and each electronic viewfinder has to be adjusted individually in the video camera. is being carried out.

Therefore, an object of the present invention is to derive an anode voltage from the secondary winding of a flyback transformer, configure this anode voltage to be adjustable, and further invert the error in the power supply voltage supplied to the primary side. By superimposing the amplified voltage on the anode voltage, the optimum focus point can be adjusted and
To provide an anode voltage adjustment circuit for a cathode ray tube that can easily and independently cancel an error in a power supply voltage supplied to the next side with a simple circuit configuration and without causing significant power loss. It is in.

[Means to solve the problem]

The cathode ray tube anode voltage adjustment circuit according to the present invention rectifies and controls the flyback pulse generated on the secondary side of the flyback transformer by controlling the switching of the power supply voltage supplied to the primary winding of the flyback transformer. The voltage obtained by smoothing is supplied to the anode of the cathode ray tube, and a correction voltage for correcting the anode voltage that causes an error in proportion to the degree of error in the power supply voltage is applied to the voltage based on the power supply voltage at a predetermined amplification degree. of the cathode ray tube by adjusting the value of the correction voltage without impairing the form in which the correction voltage is amplified at the predetermined amplification degree and superimposed on the flyback pulse. It is characterized by being configured to adjust the anode voltage.

[For production]

According to the anode voltage adjustment circuit for a cathode ray tube (CRT) according to the present invention, the anode voltage is configured to be adjustable, and when the anode voltage is initially adjusted, one of the flyback transformers
A temporary power supply voltage having a predetermined reference voltage value is supplied to the next side to set the anode voltage. Then, because the power supply voltage actually supplied to the primary side of the flyback transformer causes an error with the reference voltage value, the anode voltage supplied to the CRT causes an error with the initially set voltage value.
When the RT focus adjustment deviates from the initial setting and becomes inappropriate, the error generated in the anode voltage due to the influence of the error in the power supply voltage supplied to the primary side is canceled and the resolution becomes dependent on the power supply voltage. By removing gender,
The initially adjusted anode voltage can be maintained at a proper state at all times to easily obtain the optimum focus point of the CRT.

In addition, it is possible to omit the initial adjustment, or roughly adjust the anode voltage during the initial adjustment, and then obtain the optimum focus point of the CRT when the power supply voltage is actually supplied to the primary side of the flyback transformer. Even if you adjust the anode voltage to Always maintained in proper condition.

〔Example〕

Next, embodiments of a cathode ray tube (CRT) anode voltage adjustment circuit according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a main part circuit diagram showing a typical embodiment of a CRT anode voltage adjustment circuit according to the present invention. In FIG. 1, reference numeral 10 designates a magnetic field focusing type CRT whose electrode configuration consists of a cathode K, a first grid G1, a second grid G2 and an anode A. Further, reference numeral 12 indicates a flyback transformer, and this transformer 12
A primary side power supply voltage 10B is connected to one end of the primary winding L1, and a series circuit consisting of a transistor Q, which supplies a horizontal drive pulse to the intermediate tap, an i-direction yoke DY, and a DC blocking capacitor C1. and a resonant capacitor C2 are connected to the primary winding, and a damper diode D is connected to the other end.

is connected.

However, in the present invention, the flyback transformer 1
A tap is provided in a part of the secondary winding of 2. The voltage generated at this tap is passed through a DC blocking capacitor C1 to a rectifying diode D2. The supply voltage V to the second grid G2 is rectified via Ds and the smoothing capacitor c4.
. Configure the circuit to obtain 2. In addition, the diode D
, and a feedback resistor Rp is provided between the output line of the smoothing capacitor c4 and the low voltage side terminal of the secondary winding L2 of the flyback transformer 12, and the secondary winding L of this feedback resistor Rp is
At the connection point with the second side terminal, there is a transistor Q2. Q, ,
An adjustment port FI@16 consisting of resistors R8 to Rs, variable resistor R6, resistor R7, and Zener diode ZD is connected.

The high voltage side of the secondary ff1J winding L2 of the flyback transformer 12 is connected to the anode of the CRTIO via a voltage doubler rectifier port #114 that boosts the output of the flyback transformer.

Further, a video signal is supplied to the first grid G1 of the CRTIO via a capacitor Cs and a resistor Ra.

With this configuration, it is possible to eliminate the influence of errors caused by variations in the value of B on the power supply voltage supplied to the primary side. Further, with this configuration, it is possible to eliminate the influence of an error in the value of the primary side power supply voltage 7B caused by fluctuations in the primary side power supply voltage +B due to temperature changes or the like. Further, the voltage generated in the feedback resistor R, which is adjusted by the adjustment circuit 16, is transferred to the two of the flyback transformer 12.
CR is superimposed on the anode voltage induced in the next winding L2.
T focus adjustment can be performed appropriately.

Here, the adjustment circuit 16 is configured as follows.

The collector of the transistor Q2 in the adjustment circuit 16 is connected to the feedback resistor Rp and the secondary winding L2 of the flyback transformer 12.
Connect to the connection point with the low voltage side terminal of transistor Q,
The collector of the transistor Q2 is connected to the power supply voltage terminal B supplied to the primary side, and is also connected to the connection point between the base of the transistor Q2 and the resistor R2 via a resistor R1. The base of transistor Q2 is grounded via resistor R2. transistor Q
, are connected to the emitter of transistor Q2 via resistor R1 and grounded via resistor R4.

One end of the resistor R9 is connected to a power supply voltage element B supplied to the primary side, and the other end is grounded via a Zener diode ZD and connected to one end of a variable resistor R6. The other end of variable resistor R6 is grounded via resistor R7. The base of transistor Q3 is connected to variable resistor R6.

The operation of the adjustment circuit 16 configured as described above will be explained.

If the output voltage of the adjustment circuit 16 is Vo, and the current flowing through the feedback resistor R2 is I, then Vo - VO2I p ・RF ”
・■The base voltage of transistor Q2■8□ is Va□=
+B・ (R2/ (R+ 1 R2))...■, and the emitter current 112 of the transistor Q2 is the forward voltage between the base and emitter of the transistor Q2, Vait,
If the voltage of resistor R2 is VB4, ■E□=〈Vll□-V86□-VB4)/R3...
・It becomes ■.

Zener voltage of Zener diode ZD is V2, variable resistor R
If the adjusted resistance value of resistor R6 is R61, and the forward voltage between the base and emitter of transistor Q3 is V3, the voltage VR4 of resistor R4 is R610R? ■R4-V2 ・-VB,, ・・・
■R6+R7, where the current amplification factor of each transistor Q, Q2 is sufficiently large that the base current can be ignored, and if the transistors have the same rating, I P = I E2 + V BI3 - V 8E3
”'■ Therefore, using equations ■～■, adjust circuit 1
6 output voltage V. is expressed by the following formula.

R-R2 Vo ” VO2 (B・R3R1+R2 R61moR7 -Vz・) ・・・■R6
10R7 However, for VO2, smoothing diode C1 is sufficiently large,
It is assumed that there is no influence of errors due to variations in the value of the power supply voltage element B supplied to the primary side.

That is, it can be seen from Part 2 that the output voltage V0 is determined by the second grid voltage VO2, the primary side power supply voltage terminal B, and the Zener voltage V2 once the resistance value is determined. Therefore, if each of the above voltages is constant, the anode voltage, that is, the focus can be adjusted by adjusting the value of the variable resistor R6.

Note that the equation in parentheses (2) represents the difference in base potential between the transistors Q2 and Q, and indicates that the adjustment circuit 16 has a differential circuit configuration.

In addition, the output voltage error ΔV0 when the value of the primary rPJ power supply voltmeter 8 deviates from the reference voltage value by ΔV is calculated by the above equation
It can be calculated using the following equation.

ΔVo ”Vo CB±ΔV, )-V, (B)R2
・R.

=乎 ° ・ΔvB ・・・■(R+
+R2)・R1 Therefore, if the value of power supply voltage element B supplied to the primary side deviates from the reference voltage value by ΔVB, the effect on the secondary side anode voltage can be determined by appropriately selecting the resistance ratio in formula (■). By this,
It can be seen that cancellation can be achieved by superimposing ΔV0, which has the opposite polarity to Δv8, on the low voltage side terminal of the secondary winding L2. Furthermore, equation (2) shows that the error ΔV8 in the value of the power supply voltage 10B supplied to the primary side can be canceled independently of the adjustment of the variable resistor R6.

Here, explanation will be given by substituting specific numerical values.

Primary lFI power supply voltage ±B is 8V, secondary side anode voltage V
Let A be 2200V, the second grid voltage VG2 be 300V, and each resistance value be as follows.

RF = I MΩ, R1 = 3.9 Ω, R2 = 12 Ω, Ri = 2.7 Ω, R4 = 5.1 Ω, Rs = 1.3 Ω, Rh = 2 kΩ (R, , =O~2 kΩ), R7=1
In addition, in order to improve the temperature characteristics of the circuit, the Zener voltage (2) of the Zener diode ZD is used at a voltage such that the Zener voltage temperature coefficient is close to zero, and here Vz is set to 6V.

First, the error amount Δ in the value of the power supply voltage 10B supplied to the primary side
③ The cancellation operation will be explained. Assuming that the value of the power supply voltage 10B supplied to the primary side deviates from the normal reference voltage value by ±5%, the value of the anode voltage on the secondary side deviates from the reference voltage value of 2200V by ±110V. In the adjustment circuit 16 for each of the above values, if the value of the power supply voltage 10B supplied to the primary side has an error of ±5%, from equation (2), ΔV.

2kXIM = 壬
× 0, 4 (+12k for 3, 9) ±110
It is possible to almost cancel V and maintain a constant voltage.

Next, focus adjustment will be explained.

The value of the anode voltage is 2200V plus the output Vo of the body difference circuit 16, and the error caused by the deviation of the power supply voltage supplied to the primary side from the regular reference voltage value is canceled as described above. In addition, the potential connected to the base of the transistor Q3 is stabilized by the Zener diode ZD. The variable resistor R6 (i.e.,
It changes depending on the value of R6I), and from the equation (2), it changes in the range of o=O to 300 [V] for adjustment of Ω to O to 2. In other words, if the anode voltage of 2,200V is set as the center of the variable resistor R6, the anode voltage can be finely adjusted within the range of ±150V, so even if the focus voltage (second grid voltage) is constant, the anode voltage can be adjusted. Since the result is equivalent to relatively changing the focus voltage, focus adjustment can be realized by adjusting the anode voltage.

In this example, the zener voltage V2 is used at a voltage that makes the zener voltage temperature coefficient close to zero, and since the output voltage is determined by the resistance ratio, the temperature characteristics can be matched if the same type of resistor is used. , the temperature dependence of the adjustment circuit 16 can be made very small.

FIG. 2 shows another embodiment of the present invention in which the power supply voltage of the adjustment circuit is taken from the secondary side of the flyback transformer. In this embodiment, a coil L4 and a diode D are connected to the secondary side of the flyback transformer.
4 and capacitor C6 to generate the -B power supply, and the point that the correction voltage and adjustment voltage are superimposed on the low voltage side terminal of the secondary winding L2 for anode voltage is basically the same as the first one. Since it is the same as the embodiment shown in the figure, detailed explanation will be omitted. Regarding the same components as in Figure 1,
The same reference numerals are given.

〔Effect of the invention〕

According to the above-mentioned implementation, by superimposing the output of the differential configuration adjustment circuit on the low voltage side terminal for the anode voltage of the secondary winding, the power supply voltage supplied to the primary side is adjusted to the regular reference voltage. It is possible to easily suppress the error generated in the anode voltage due to the influence of the error due to deviation from the value and adjust the focus independently of the screen size, brightness, and contrast.

As described above, according to the present invention, errors due to the power supply voltage actually supplied to the primary side deviating from the regular reference voltage value and fluctuations in the power supply voltage supplied to the primary side due to temperature changes, etc. Since the influence of errors can be removed, there is no fluctuation in the focus point, and therefore the resolution of the CRT is stable without being affected by the above-mentioned errors.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of a cathode ray tube (CRT) anode voltage adjustment circuit according to the present invention, and Fig. 2 shows a case where the power supply voltage of the adjustment circuit is configured by the secondary winding of a flyback transformer. FIG. 3 is a diagram showing another embodiment of the present invention. 10...CRT 12...Flyback transformer 14...Voltage doubler rectifier circuit 16...Adjustment circuit Ll...Primary winding R2, R3, R4...Secondary winding Q, , C2, Q,...Transistor C+, Cs...DC blocking capacitor C2...Resonance capacitor C4...Smoothing capacitor Cs, C6...Capacitor DY...In-plane yoke RF...Feedback resistor R1~Rs, R7...Resistor R6...Variable resistor ZD...Zena diode DJ...Damper diode

Claims (1)

[Claims] (1) The voltage obtained by rectifying and smoothing the flyback pulse generated on the secondary side of the flyback transformer by controlling switching of the power supply voltage supplied to the primary winding of the flyback transformer is applied to the cathode ray tube. A correction voltage that is supplied to the anode and that corrects an anode voltage that causes an error in proportion to the degree of error in the power supply voltage is formed by amplifying a voltage based on the power supply voltage at a predetermined amplification degree. The anode voltage of the cathode ray tube is adjusted by superimposing it on a flyback pulse and adjusting the value of the correction voltage without impairing the form in which the correction voltage is amplified at the predetermined amplification degree. A cathode ray tube anode voltage adjustment circuit featuring: