JPS593366Y2 - Signal level balance adjustment circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a signal level balance adjustment circuit, and in particular, the present invention uses a single amplifier to adjust the frequency of two inductive loads having approximately the same impedance by adjusting the oscillation between the two loads. The present invention aims to provide a balance adjustment circuit that can supply signals without changing characteristics and with less voltage loss caused by the addition of the circuit.

As an example of supplying a signal to two inductive loads having substantially the same impedance, a recording amplifier of a simple video tape recorder (hereinafter referred to as VTR) will be explained below.

Conventionally, the output stage of the recording amplifier 1 of a simple VTR and the two heads HA and HB have been connected via a capacitor C, as shown in FIG. 1, or via a variable resistor, as shown in FIG. There was something connected through.

For those configured as shown in FIG. 1, the head HA,
Even if there was a difference in the optimum recording current value due to the different characteristics of HBs, there was no way to correct this.

Therefore, the individual capabilities of the heads HA and HB cannot be fully utilized, and the S/N ratio of the luminance signal may deteriorate.

Further, in the configuration as shown in FIG. 2, it was possible to correct the imbalance between the optimum recording currents of the heads HA and HB using the variable resistor 2 in the output stage.

However, there is a drawback that the voltage loss due to the resistance is large, and changes in the resistance value affect the frequency characteristics of the recording current.

In order to solve this problem, in the configuration shown in Figure 1, it is sufficient to use heads HA and HB with exactly the same characteristics, but considering the yield rate and aging of the heads, In reality, it is often extremely difficult to do so.

The present invention provides a solution to these problems, and embodiments thereof will be described below with reference to the drawings.

As shown in FIG. 3, the present invention provides a coil 3 with a variable intermediate tap, which allows the intermediate tap to be selected from any position at the final stage of the recording amplifier 1 and has a high coupling coefficient, to change the intermediate tap position. This attempts to adjust the balance of recording currents provided to HA and HB.

Next, a detailed explanation will be given based on the influence of inserting the variable intermediate tapped coil 3.

In Fig. 3, when the movable tap C is set to an arbitrary position, the inductances between a and C of the coil and between b and C of the coil are respectively L, (H), and L2.CH, and the head HA (impedance Z1) and head HB (impedance Z2), respectively. ■Set it as 2.

First, let us explain the case where the characteristics of the heads HA and HB of both channels A and B are exactly the same.The fact that the characteristics of the heads HA and HB of both channels A and B are exactly the same means that they have the same impedance, Since the optimum recording current is the same, the tap position of the variable intermediate tapped coil can be set at the midpoint of the coil 3.

Therefore, L1=L2. ■,=■2. The magnetic flux generated by this time is φ1. If the magnetic flux generated by L2 is φ2, φ□=φ2 [- indicates that the direction is opposite]
holds true.

This is because the value of the inductance L of the coil 3 is proportional to the square of the winding N of the coil, and the magnetic flux φ generated by the inductance L is proportional to the number of turns N of the coil 3 and the current I flowing through the coil.
is proportional to the product of

Therefore ■□2I2. If L1=L2 (N1=N2 since the same coil is divided), φ□=Consists.

At this time, φ1 and φ2 have the same strength and opposite directions, and because the coil's line-adjacent coupling coefficient is high, they cancel each other out.

Therefore, since Ll and L are equal to non-existence, even if a coil is inserted, it has no effect on the circuit.

Next, a case where there is a difference between the heads HA and HB between the two channels A and 8 and the optimum recording current values are different will be described.

Due to the difference between heads HA and HB, the optimum recording current value may be 1
1>I2, and even if the variable intermediate tap position is adjusted to be set a little away from the midpoint of the coil, most of the components of inductances L1 and Ll will be lost due to the self-generated mutual magnetic flux. In order to equalize the loss, the voltage drop due to the coil is extremely smaller than the voltage drop when the recording current is adjusted by inserting coils into the heads HA and HB, even if the coupling coefficient is low.

Furthermore, considering the case where the recording current can be adjusted at the uppermost end as shown in FIG. However, no effect was observed due to the insertion of the coil.

In addition, the recording current in this case is adjusted (the respective voltages applied to the heads HA and HB are adjusted).

) is inductive, just like the load (head), so as is clear from the characteristics of frequency f and recording current (2) shown in Fig. 4, the voltage drop element is inductive, so the voltage drop is centered around the standard value (a), as is clear from the characteristics of frequency f and recording current (2) shown in Figure 4.

Since the recording current follows within a certain range, it is possible to balance the recording current while keeping the frequency characteristics of the circuit almost constant.

As described above, according to the present invention, a single amplifier and two loads are connected via a variable intermediate tap coil having a high coupling coefficient between the first and second inductances divided by the variable intermediate tap. Because they are combined, the two attached heads can be set to the optimum recording current for each without affecting the frequency characteristics of the circuit and with less voltage loss, making it possible to make the most of the capabilities of each head. .

The present invention is effective not only for recording amplifiers of simple VTRs, but also for circuits that supply signals to two or more inductive loads.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a first conventional recording amplifier, and Figure 2 is a circuit diagram of a second conventional recording amplifier.
FIGS. 3 to 5 show an embodiment of the present invention, FIG. 3 is a recording amplifier circuit diagram, and FIG.
The figure is a recording current frequency characteristic diagram, and FIG. 5 is a recording width amplifier circuit diagram showing the extreme state of adjustment. 1...Amplifier, 3...Coil, A...
...A channel, B...B channel,
HA, HB...head, C...capacitor, I□, I2...recording current, Ll, Ll
・・・・・・Coil inductance, N1. N2...
...Number of turns of coil, φ1. Mo: Generated magnetic flux.

Claims (1)

[Claims of Utility Model Registration] A signal is supplied from a single amplifier to two inductive loads having approximately the same impedance. In the circuit, the first and second are divided by a variable intermediate tap.
A coil with a variable intermediate tap having a high coupling coefficient between the inductances is provided, the variable intermediate tap of this coil is connected to the amplifier output, and each terminal of the first and second inductances other than the variable intermediate tap is connected to the terminals of the first and second inductances, respectively. Signal level balance adjustment circuit connected to two loads.