JPH04196684A - Coil drive circuit - Google Patents

Abstract

PURPOSE:To correct the linearity of a deflection current over a wide range by means of a circuit able to be circuit integration by connecting a negative resistance circuit in series with a coil and setting a negative resistance to be almost cancelled with the resistance of the coil. CONSTITUTION:A negative resistance circuit 1 consists of two operational amplifiers 2, 3 connecting a positive power supply and five resistors R1-R5 is connected in series with a coil 6 and a negative resistance of the negative resistance circuit 1 is set to be a value almost cancelled by a resistance RH of the coil 6. Since the resistive component of the coil is cancelled, the deflection current is not saturated but linear. Thus, the correction range of the linearity is wide and the adjustment for each receiver is not required and the coil drive circuit is realized, in which the productivity is high, the circuit integration is attained and which is advantageous for miniaturization of the receiver with simple configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a coil drive circuit, and more particularly to a coil drive circuit that can be used as a drive circuit for a horizontal or vertical deflection coil in a television receiver.

BACKGROUND OF THE INVENTION FIG. 3 shows a circuit diagram of an example of a conventional coil drive circuit used to drive a horizontal deflection coil of a television receiver. In the figure, Hs is a horizontal synchronizing signal, and Vcc is a power supply voltage. The base of the switching transistor Q is connected to the horizontal synchronizing signal input terminal via a resistor R11, the collector is connected to Vcc via the primary winding L1 of the transformer, and the emitter is connected to ground. A resistor RIO is connected to the base and emitter of Q. A capacitor C is connected to L in parallel.

The cathode of the dump diode D is connected to the collector of Q.
They are connected to the anode or the emitter of Q, respectively. The collector of the transistor Q is also equipped with a figure-8 correction capacitor Cs, a resistance value R, and an inductance L8 for correcting the contraction in the center of the horizontal scanning line and the expansion at both ends using series resonance with the deflection coil. horizontal deflection coil 6, R,
A saturable reactor Lc biased by a direct current magnetic field from a permanent magnet is connected in series and grounded.

One end of the secondary winding is connected to ground, and it is electromagnetically coupled with L to output an output voltage v0, supplying a high voltage power source such as an anode power source for a cathode ray tube.

In FIG. 3, the base voltage of the switching transistor Q is set to v3. ■Collector voltage. , the base current is IB+
Let the collector current be 1°. Further, the current flowing through the damper diode D is assumed to be ID+, the current flowing through the horizontal deflection coil 6 is expressed as i, and the voltage generated across the horizontal deflection coil 6 is expressed as V.

Each voltage and current waveform is as shown in FIG.

After the horizontal synchronizing signal Hs is voltage-divided by resistors R and R3°, it is applied to the base of the transistor Q as a voltage shown as VB in FIG. to control switching. Also, the base current of transistor Q is as shown by IB in FIG.
The waveform corresponds to Vll.

The collector voltage VC of transistor Q is
When the transistor Q is on, the voltage is OV, and when the transistor Q is off, the voltage is as shown in FIG.

Further, by turning on the transistor Q, the collector current of Q increases linearly from time t, as shown by IC in FIG. 5, and by turning off the transistor Q at time t2, the collector current of Q increases linearly as shown by IC in FIG. quickly becomes zero. While transistor Q is off, no current flows through IC.

The damper diode current becomes conductive when the transistor Q is turned on at time t3, as shown by ▪ in FIG. 5, and a reverse current flows which decreases linearly with time, and becomes zero at time t4. Io does not flow while transistor Q is off.

The deflection current 12 flowing through the horizontal deflection coil 6 increases linearly with time from time t1 when the transistor Q is turned on. When the transistor Q is turned off at time t2, the magnitude of the deflection current i decreases with time, rapidly flows in the opposite direction, and reaches a negative peak at time t3. When the transistor Q is turned on at time t3, the deflection current ia decreases linearly with time and reaches O at time t4.

The voltage Va across the deflection coil 6 becomes a negative voltage equal in magnitude to the power supply voltage Vcc when the transistor Q is on, and gradually increases when the transistor Q is turned off at time t2, resulting in a deflection current iy. It reached its peak at the time of Cero,
Next, it gradually decreases and reaches a negative voltage equal to the power supply voltage at time t3.

When Lc is not inserted in the circuit, the horizontal deflection current ia becomes an exponential saturation curve as shown by the broken line in the figure. Therefore, the horizontal scanning line shrinks on the right side of the screen and stretches on the left side.

FIG. 4 is a diagram showing the relationship between the current flowing through the saturable reactor L0 biased by a DC magnetic field generated by a permanent magnet and the self-inductance. The linearity of the deflection current lA is corrected by utilizing the fact that the self-inductance changes depending on the degree of saturation of the current flowing through Lc.

That is, as shown in the figure, since the current is small at the end of the scan (indicated by A in the figure), the inductance of the saturable reactor Lc becomes large, and the deflection current ia is made small. At the end of scanning (indicated by B in the figure), the current is large, so the inductance of the saturable reactor Lc becomes small, and the deflection current ia does not become very small. As a result, the deflection current i
, is corrected linearly.

Problems to be Solved by the Invention According to the conventional coil drive circuit described above, in order to correct the distortion of the horizontal scanning line, a saturable reactor Lc biased by a DC magnetic field from a permanent magnet is used. According to this method, the saturable reactor L. Since the ferrite core was wound with a wire and equipped with a permanent magnet, it was impossible to integrate it into an IC, and the drive circuit also tended to be large.

In addition, in order to adjust the linearity, it was necessary to adjust the bias magnetic field for each receiver while viewing an adjustment chart on the screen of the receiver, making the process complicated. Furthermore, since the adjustment is performed by changing the bias magnetic field, the range that can be corrected is also narrow.

The present invention has been made in view of the above-mentioned drawbacks, and has a wide linearity correction range, does not require adjustment on the receiver side, has high productivity, can be integrated into an IC, and has a coil drive that is advantageous for miniaturizing the receiver. The purpose is to provide a circuit with a simple configuration.

Means for Solving the Problems In order to solve the above-mentioned problems, in the present invention, a negative resistance circuit is connected in series with the coil in a coil drive circuit that drives the coil with a synchronization signal to cause a sawtooth current to flow through the coil. The negative resistance value of the negative resistance circuit was set to a value that substantially canceled out the resistance value of the coil.

Since the resistance of the coil is canceled by the negative resistance value of the negative resistance circuit, the deflection current does not saturate (becomes a straight line).

Embodiment FIG. 1 shows a circuit diagram of an embodiment of the present invention. In the figure, the same components as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 1, l is a negative resistance circuit consisting of two operational amplifiers 2.3 and five resistors R1 to R5 powered by a positive power supply.

The operational amplifier 2 is connected to the power supply voltage Vcc and ground, and one end of the horizontal deflection coil 6 is connected to the inverting input terminal. Further, a resistor R4 is connected between the inverting input terminal and the output terminal, and a resistor R2 is connected between the non-inverting input terminal and the output terminal. The non-inverting input terminal is also connected to one end of a resistor R5.

The output terminal of another operational amplifier 3 is connected to the other end of the resistor R5. The operational amplifier 3 has a power supply voltage Vcc.
and ground or connected. The inverting input terminal and the output terminal are connected to each other. Non-inverting input terminal and power supply voltage V
A resistor R3 is connected between ccO and a resistor R4 is connected between the non-inverting input terminal and ground.

Here, if the input impedance of the negative resistance circuit 1 is Zll as shown in the figure, then the impedance of the horizontal deflection coil 6 is Z. Then, Z, = jωLH + RH (2) Then, by selecting the values of R,, R2 and R, respectively, Zs + Z++ = jωLo (5
), the resistance component is canceled out, and the horizontal deflection coil 6 becomes an ideal coil with only an inductance component.

Therefore, the horizontal deflection current ia exhibits linearity without being saturated as in FIG. 5, and it is possible to eliminate expansion on the left side of the screen and contraction on the right side of the screen.

FIG. 2 shows a circuit diagram of another embodiment of the invention.

In the figure, the same components as those in FIG. 4 are denoted by the same reference numerals, and the explanation thereof will be omitted. In FIG. 2, 4 is a negative resistance circuit consisting of one operational amplifier 5 using two positive and negative power supplies and three resistors R1 to R3.

The operational amplifier 5 is connected to a positive power supply voltage Vcc and a negative power supply voltage Vss. One end of the horizontal deflection coil 6 is connected to the non-inverting input terminal, and a resistor R6 is connected between the non-inverting input terminal and the output terminal, and a resistor R7 is connected between the inverting input terminal and the output terminal. There is. A resistor R is connected between the output terminal and ground.

Here, if the input impedance of the negative resistance circuit 4 is z12 as shown in the figure, then from equation (2), the values of the resistors Ra, R7, and R8 are respectively selected so that there are two resistors. By doing so, Z)l +Z12= jωL+
(9), the resistance bones of the circuit are canceled out, and the horizontal deflection coil L becomes an ideal coil with only an inductance component.Therefore, the horizontal deflection current 1 shows linearity, and the horizontal distortion of the screen It is possible to remove

According to the circuit of the above embodiment having two positive and negative power supplies, the horizontal deflection current can be corrected by a circuit that can be integrated into an IC with a very simple configuration of only one operational amplifier and three resistors.

As explained above, according to this embodiment, the linearity of the deflection current can be corrected over a wide range by changing the resistance value using an IC-compatible circuit without using a saturable reactor. It is ideal for the deflection coil drive circuit of hand-held cathode ray tubes such as electronic viewfinders.

However, the actual adjustment involves not only the resistance of the horizontal deflection coil, but also the primary winding of the other transistors Q and lance.
Is it necessary to adjust the resistance value including the loss of capacitor C etc.?

Effects of the Invention As described above, according to the present invention, since the deflection coil can be configured with only an inductance component without using a saturable reactor, it is possible to use an IC, which is advantageous for downsizing the receiver, and also improves linearity. It has the advantage that the correction range can be widened, and productivity can be improved because adjustments for each receiver are not required.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of one embodiment of the present invention, Fig. 2 is a circuit diagram of another embodiment of the invention, Fig. 3 is a circuit diagram of the prior art, and Fig. 4 is a circuit diagram of another embodiment of the present invention.
The figure is a characteristic diagram of a saturable reactor for explaining the correction principle of the prior art, and FIG. 5 is a current-voltage waveform diagram showing the operation of the conventional circuit. 1.4... Negative resistance circuit, 2, 3.5... Operational amplifier, 6... Horizontal deflection coil.

Claims (1)

[Claims] In a coil drive circuit that current drives a coil using a synchronization signal to flow a sawtooth current through the coil, a negative resistance circuit is connected in series with the coil, and the negative resistance value of the negative resistance circuit is set as the resistance of the coil. A coil drive circuit characterized in that the coil drive circuit is set to a value that substantially cancels out the current value.