JPH0463065A - Horizontal deflection centering circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a horizontal centering circuit for adjusting the horizontal raster position of a television receiver.

[Summary of the Invention] The horizontal centering circuit of the present invention can vary from a positive DC voltage to a negative DC voltage on the secondary side of a horizontal output transformer that generates a sawtooth current that supplies a horizontal deflection coil. In the horizontal centering circuit, the raster horizontal position of the picture tube can be adjusted by providing a floating power supply circuit and supplying the output of the floating power supply to a horizontal deflection coil, in which the midpoint voltage and output of the floating power supply are adjusted. The voltages are divided by resistors and used as input signals to a differential amplifier, and the output of the differential amplifier controls the input voltage of the current amplifier that constitutes the floating power supply, thereby changing the DC current flowing through the horizontal deflection coil. With this structure, centering adjustment can be safely performed by a low voltage circuit, and automatic adjustment by a microcomputer is also possible.

[Prior art j] Monitor televisions and day play equipment that display video signals using cathode ray tubes (CRTs) are usually provided with a horizontal centering circuit to adjust the horizontal raster position of the monitor image, and to correct the unbalance of the horizontal deflection coil. or CRT
The configuration is such that it is possible to adjust the deviation in the horizontal raster position caused by variations in the horizontal raster position.

FIG. 3 is a circuit diagram showing an example of such a horizontal centering circuit, in which 10 is a horizontal drive circuit comprising a switching transistor Q, a damper diode D, and a resonant capacitor C, HOP is a horizontal pressure quadrangle consisting of a flyback transformer, etc. 20 indicates a floating power supply consisting of a rectifier circuit consisting of rectifier diodes D, D, smoothing capacitors C, C2, a variable volume VR, and a current amplifier consisting of transistors T1 and T2.

The midpoint voltage of this floating power supply 20 is connected to the hot terminal of the primary coil L1 of the horizontal pressure cadence HOP,
The output is supplied to the horizontal deflection coil DY-H via a choke coil ch.

Note that Cs is a capacitor for character-8 correction, and Ql is a transistor for pin distortion correction, but since these functions are not directly related to the present invention, detailed explanation thereof will be omitted.

When the switching transistor Q is on/off controlled by the horizontal synchronous switching pulse HD supplied to the horizontal drive circuit IO, as is well known, the primary side of the horizontal pressure cadence HOP and the horizontal deflection coil DY
A sawtooth wave current flows through -H and scans the electron beam of a CRT (not shown) in the horizontal direction.

Also, at this time, a flyback pulse is induced in the secondary coil of the horizontal pressure cadence HOP, and when this flyback pulse is rectified by the rectifier diodes D, , D,
Smoothing capacitors C, C2 are charged with DC voltages of 10E and -E, respectively.

Therefore, when the positive DC voltage E1 and the negative DC voltage E2 are divided by a variable volume VR and supplied to the transistors T, T2, a DC current flows from the emitter output to the choke coil ch and the horizontal deflection coil DY-H1 horizontal output. It flows through the primary coil of the quadrance HOP as shown by the dotted line.

The direction of this DC current i changes depending on the position of the variable volume VR, so when the value and direction of this DC current are adjusted, the position of the horizontal raster moves left and right on the monitor screen, and the centering can be adjusted. I can do it.

[Problem to be Solved by the Invention 1] By the way, since the flyback pulse induced by the horizontal voltage cadence HOP reaches several KV to several tens of KV, the floating power supply 20 is located entirely within the high voltage printed circuit board. Therefore, in order to adjust the variable volume VR disposed therein, it is essential to use an insulated driver.

In addition, in such a circuit, horizontal centering adjustment performed at the factory during manufacturing is extremely dangerous, and automatic computer-based adjustment, which has been done in recent years, cannot be applied to centering adjustment, making it impossible to automate the manufacturing process. There is a problem.

Means for Solving Problem E 1 The present invention has been made in view of such problems.
The midpoint voltage and output voltage of a conventional floating power supply are divided by resistors and drawn out, for example, to a circuit board separated from the floating power supply circuit, and these two voltages are configured to be supplied to a differential amplifier as differential inputs. and,
The input voltage of the current amplifier constituting the floating power supply is controlled by the output of the differential amplifier.

[Function] The current amplifier input of the floating power supply is controlled by a differential amplifier that compares the voltage obtained by dividing the current output of the floating power supply and the voltage obtained by dividing the midpoint voltage of the floating power supply. This makes it possible to place a differential amplifier for centering adjustment on a low-voltage circuit board, and it becomes possible to control the current output of the floating power supply using a normal driver or computer output.

[Embodiment 1] FIG. 1 shows a horizontal centering circuit according to the present invention, and the same parts as in FIG. 3 are given the same reference numerals.

In this figure, the part 30 surrounded by the dashed line shows the centering adjustment circuit, which includes the differential amplifier OP and the output transistor T.
3, and voltage dividing resistors r1 to r4.

Note that a horizontal centering voltage H·CENT is supplied to one input terminal of the differential amplifier OP via a resistor R.

The horizontal centering voltage H.CENT is supplied from a control section 31 and a D/A converter 32 which output data indicating the center position in response to an external control signal.

The centering adjustment circuit 30 has the output voltage of the floating power supply 20 divided by resistors r+ and r2,
At the same time as it is supplied to the inverting input terminal of the differential amplifier OP,
The midpoint voltage of the floating power supply 20 is the resistance r s +
The voltage is divided by r4 and supplied to the non-inverting input terminal of the differential amplifier OP.

The output of the differential amplifier OP controls the pace voltage of the transistors T, T2 forming the current amplifier via a common base type output transistor T3 and a resistor r5.

In the circuit of this embodiment, for example, resistor r1 and resistor r
3 are equal, and if the resistors r2 and r4 are set equal, the output voltage E of the floating power supply 20. and the midpoint voltage Ec are equal, and the current flowing through the transistors T and T2 becomes almost 0. However, if the centering voltage H CENT is supplied to the centering adjustment circuit 30 and the balance condition of the differential amplifier OP shifts (E, > Ec or E.<EC, and the current flowing through either the transistor T3 or the transistor T2 flows through the choke coil ch and the horizontal deflection coil DY-H, and the horizontal raster is moved in the left-right direction, resulting in centering. Adjustments will be made.

In addition, in the horizontal centering circuit according to this embodiment, when the absolute voltage (with respect to ground voltage) of the midpoint voltage EC of the floating power supply 20 fluctuates, the centering adjustment circuit 30 operates as a negative feedback circuit, so that the centering current does not fluctuate. There is a characteristic that it does not.

That is, when the floating power supply 20 is controlled by the grounded centering adjustment circuit 30, even if the power supply voltage element B fluctuates, both input terminals of the differential amplifier OP operate so as to have the same voltage. Midpoint voltage EC and output voltage E. There is an advantage that the relationship between the two does not change and the centering point does not change.

Note that the output transistor T3 may be omitted depending on the type of differential amplifier OP.

FIG. 2 is a circuit diagram showing another embodiment of the present invention. In this circuit example, a differential power amplifier POP is used in the floating power supply 20B instead of the transistors T, , T2, and the power amplifier POP is operated as a current amplifier.

Further, the centering adjustment circuit 30B includes a pair of transistors T4. T5 makes it an emitter-coupled differential amplifier,
The input voltage of the power amplifier POP is controlled by the collector current of the transistor T5.

Also, since the ground potential of this centering adjustment circuit 30B is connected to a negative voltage (-12V), for example, a resistor r
+ = r 3 = 150 KΩ, r 2 = r
When setting a = 12Ω and +E = 150V, the centering voltage H-CENT is almost balanced with the ground voltage,
There is an advantage that the centering voltage H-CENT can be easily supplied.

[Effects of the Invention] As explained above, the horizontal centering circuit of the present invention includes a centering adjustment circuit that operates differentially with respect to a floating power supply that supplies a current for centering correction, and a floating power supply to the centering adjustment circuit. Since the midpoint voltage and output voltage of the power supply are configured to be divided and supplied, centering adjustment is performed within the low voltage wiring circuit.

Therefore, a low-voltage external signal can be used as the centering adjustment voltage, which is advantageous in that the manufacturing process is labor-saving and adjustment service can be easily performed.

Furthermore, since the centering adjustment circuit also serves as a feedback circuit for the floating power supply, there is an effect that the centering current is stabilized.

FIG. 1 is a circuit diagram showing one embodiment of the horizontal centering circuit of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, and FIG. 3 is a circuit diagram showing a prior art horizontal centering circuit. It is.

In the figure, 10 is a horizontal drive circuit, 20 is a floating power supply, 30 is a centering adjustment circuit, DY-H is a horizontal deflection coil, H-CENT is a centering adjustment voltage,
HOP indicates a horizontal output transformer.

[Brief explanation of drawings]

Claims (1)

[Claims] A rectifier circuit that generates a positive first voltage and a negative second voltage is provided on the secondary side of a horizontal output transformer that generates a sawtooth wave current to be supplied to the horizontal deflection coil; and a rectifier circuit that generates a positive first voltage and a negative second voltage; Horizontal deflection centering, wherein a floating power supply circuit is configured by current amplifier means capable of selecting an intermediate voltage between the first voltage and the second voltage, and an output of the current amplifier means is supplied to the horizontal deflection coil. In the circuit, the midpoint voltage of the floating power supply and the output voltage are divided by resistors and supplied to both input terminals of a differential amplifier, and the input voltage of the current amplifier is controlled by the output voltage of the differential amplifier. A horizontal deflection centering circuit characterized by comprising: