JPS5827906B2 - Magnetic bubble memory drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving circuit for a rotating magnetic field used for transferring magnetic bubbles.

Transfer of magnetic bubbles requires a magnetic field that rotates within the plane of the magnetic thin film where the magnetic bubbles exist, that is, a rotating magnetic field.

To obtain such a rotating magnetic field, a pair of mutually orthogonal coils wound around a magnetic bubble requires a sine wave drive current having a phase difference of 90 degrees.

Furthermore, such a driving current can be obtained by, for example, connecting a coil and a capacitor in series and causing series resonance.

FIG. 1 shows a conventional magnetic bubble memory drive circuit forming a series resonant circuit.

A coil 1 wound around a magnetic bubble element has one end grounded via a capacitor 2 forming a series resonant circuit together with the coil 1, and the other end connected to the emitter of a transistor 3, which is a low impedance switching element, and a transistor 4. connected to the connection point.

Transistors 3 and 4 are connected in cascade between a power supply 5 and ground, and are turned on alternately by supplying a control signal to each base from a circuit (not shown).

During this on period, coil 1 and capacitor] The period is /2 of the period of the series resonant frequency due to 2.

It is clear that a sine wave at the resonant frequency flows between the coil 1 and the capacitor 2 by turning on the transistors 3 and 4.

Incidentally, the rotating magnetic field repeats an operation in which it is not generated when the magnetic bubble is not transferred, and is generated when the magnetic bubble is transferred.

In this case, it is preferable that the rotating magnetic field be generated without any transient response even at the start of operation.

For this purpose, it is necessary to make the operation start point correspond to the zero current point of the coil 1 during series resonance so that the capacitor 2 is charged to the peak of the negative voltage.

This is a negative bias power supply and includes power supply 7 and capacitor 2.
This is achieved by turning on the transistor 6 connected between the two.

The resistor 8 connected in parallel to the transistor 6 may be any resistor that supplies a current equal to canceling the leakage current so that the charging voltage of the capacitor 2 does not decrease (absolute value) after the capacitor 2 is negatively charged. In order not to lower the Q of the resonant circuit, the number of Ω to several hundred Ω is usually used.

Further, the transistor 9 connected in parallel to the coil 1 is
This is a transistor that is turned on in order to rapidly dampen the back electromotive force of the coil 1 when the rotating magnetic field is removed.

A more detailed explanation of the conventional magnetic bubble memory drive circuit described above can be found in Japanese Patent Application No. 52-79829 (Japanese Unexamined Patent Publication No. 54-02
No. 5128).

A drawback of such conventional circuits is that they have a large number of transistors.

This requires a transistor that shorts the coil and quickly stops the rotating magnetic field.

The present invention has been made to improve the drawbacks of conventional circuits.

The present invention aims to reduce the number of elements in a magnetic bubble memory drive circuit, thereby simplifying the circuit configuration.

The magnetic bubble memory drive circuit of the present invention includes a diode whose cathode is connected to one end of a coil constituting a series resonant circuit, that is, a drive current source, the other end of the diode is connected to a bias power source, and the other end of the coil is connected to a bias power source. When the rotating magnetic field is removed by connecting to the bias power supply through a transistor, the counter electromotive force of the coil is rapidly damped by the transistor and the diode, and the capacitor is charged with the voltage of the bias power supply.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows a diagram of a magnetic bubble memory drive circuit which is an embodiment of the present invention.

In explaining FIG. 2, the same parts as in FIG. 1 are given the same numbers to clarify the correspondence with the conventional circuit.

In FIG. 2, voltage E.

Transistors 3 and 4 are connected in series in cascade between a power supply 5 and ground, the bases of transistors 3 and 4 being connected to a circuit (not shown), as shown in FIGS. 3a and b, as will be explained in detail below. Such on/off control is performed, and it operates as a driving power source that supplies positive voltage pulses.

A connection point between the transistors 3 and 4 is grounded via a coil 1 and a capacitor 2 forming a series resonant circuit, and a diode 10 is connected to the connection point with a cathode.
It is connected to a power supply 7 which supplies a bias of voltage -E via.

A connection point between the coil 1 and the capacitor 2 is connected to a power source 7 via a transistor 11 and a resistor 8, which connect the emitter to the connection point.

Next, the operation shown in FIG. 1 will be explained with reference to the waveform diagram shown in FIG.

As shown in FIGS. 3a and 3b, transistors 3 and 4 are turned on and off alternately so that they are out of phase by 180 degrees.

That is, when transistor 3 is on, transistor 4
is off.

Assuming that the capacitor 2 has already been charged to a voltage -E by the power source 7, the transistor 3 is turned on and a current 2, as shown in FIG. 3d, begins to flow through the coil 1.

When the current {circle around (2)} reaches its peak at the resonant frequency determined by the coil 1 and capacitor 2, the transistor 3 is turned off and the transistor 4 is turned on instead.

In this case, since the transistor 11 is controlled to be off, the current 2 in the coil 1 starts to decrease and becomes zero.
Further, it continues to increase to a negative peak.

On the other hand, the voltage of capacitor 2 ■.

starts from the voltage -E, and as shown in Figure 3e, the current ■
, it becomes a sine wave delayed by 90 degrees.

When capacitor 2 reaches voltage -E, transistor 1
1 is turned on, capacitor 2 becomes and maintains voltage E.

If the inductance and resistance of the coil 1 are L and R, respectively, and the saturation voltages of the transistors 3 and 11 are ignored, the current {circle around (2)} is expressed by the following equation.

While the transistor 3 is on, the current ■, continues to increase, and when the transistor 3 turns off, the current ■,
is at a value greater than the normal peak value.

After this point, the current (2) gradually decreases, and the back electromotive force of the coil 1 is absorbed by the closed loop formed by the transistor 11 and the diode 10 and becomes zero.

In this case, the fluctuation of the current ■, which exceeds the steady state peak due to the turning on of the transistor 1, does not have an adverse effect on the magnetic bubble, but rather the operating range of the rotating magnetic field is reduced due to the cessation of the current ■. This is a desirable result of compensating for the

Note that if transistor 1 is not turned on, the waveform will be as shown by the dotted line in the figure, and the voltage will be V.

and current ■, will eventually become zero.

In addition, in the above explanation, the transistors 3 and 11 are turned on at the same time, but the operation of the present invention is not limited to this. Any time is fine if you have it.

The current {circle around (2)} has a waveform before reaching the maximum value of the sine wave, and increases further when transistor 1 is turned on, and decreases when transistor 3 is turned off.

Further, the value at the time when the current IX is stopped can be easily changed to a larger value by increasing the on period of the transistor 3.

As described above, the present invention has the effect of simplifying the circuit configuration and control.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional magnetic bubble memory 1 drive circuit,
Fig. 2 is a circuit diagram showing one embodiment of the present invention, and Fig. 3 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a waveform diagram illustrating the operation shown in FIG. 1... Coil, 2... Capacitor, 3
,4,6゜9.11...transistor, 5,7
...Power supply, 8...Resistance, 10...
··diode.

Claims (1)

[Claims] 1. A coil and a capacitor are connected in series, one end of the coil is connected to a drive current source, one end of the capacitor is grounded, and a sine wave current is generated by series resonance between the coil and the capacitor. In a magnetic bubble memory 1 drive circuit that obtains a magnetic field for transferring magnetic bubbles, a diode connected with opposite polarity between one end of the coil and a bias power source, and a diode connected between the other end of the coil and the bias power source. A magnetic bubble memory and a drive circuit, characterized in that the diode and the turned-on transistor constitute a circuit that absorbs the back electromotive force of the coil. 2. The magnetic bubble memory drive circuit according to claim 1, wherein the diode has a cathode connected to a connection point between a drive current source that supplies a positive voltage pulse and the coil.